（二）technical externalities.

Technical externalities of industry cluster effect is obvious. We through to the predecessors' research results, and the current situation of the cluster of new economic conditions, that generally has the following categories: (1) technical spillover. Due to enterprise cluster, a certain technical knowledge gained by the enterprises technological innovation information (management style, new technology, new technology, etc.), will have a big part of spillover (general knowledge reason is non-exclusive and the free flow of skilled workers and companies are enjoying the informal and formal communication), as enterprises in the cluster of public knowledge and technology. These technical knowledge is the enterprise location function of the distance, only on the spatial cluster of enterprises can get, and once leave the cluster will be lost. Based on the pursuit of technology spillovers, the enterprise has the tendency of the cluster, industry on the geographical spatial agglomeration, thus forming industrial cluster. Industry through innovation not only from the technical monopoly of the excess profits, and the group effect the formation of a common technical standards, to further expand monopoly advantage. Industrial cluster using geographical proximity, formal or informal cooperation, technical standard easily recognized within the industry cluster, adopted by the enterprise, the more the greater the external effect of industrial cluster. (2) dry while learning. According to the arrow to establish a model of "dry while learning" dry while learning is the product of experience, experience with increasing productivity. With the accumulation of experience, the unit product cost decrease with the total production. The image of the "dry while learning" the outline of the cluster companies enjoy a aspect of technical externalities. In general, most of the enterprise's innovation latecomers, reason is the enterprise strength, management level and market opportunities, etc.), but among cluster enterprises, because can accurately and quickly grasp the technical change information (including technical knowledge, technology, market), and part of the new technology in the innovation out after will spread through various channels to nearby enterprises, these enterprises can free (or cheap) for the part of the technology or management experience and technology, in their own production process, production, while learning, digestion, and innovation. This saves the enterprise technology innovation elements of investment, technology innovation and save the time, and can from dry while you are learning to improve productivity and reduce cost, so as to achieve the rapid expansion of enterprise itself. Industry cluster can have the motive force of sustainable development, and is that industrial cluster is a learning area, within the cluster innovation network and for the embeddedness enterprises in the group of mutual learning.

All in all, externality produced industrial agglomeration centripetal force. In the industrial cluster effect, due to accumulation of economic externalities, is just a companion, passive and static effect, its strength is limited. The biggest effect of industrial cluster, the common action of the main action, it is a kind of active, dynamic, persistent effect. From the static perspective, the external effect of industrial agglomeration makes enterprises can from the region in the same industry other enterprise or other enterprises in different industries directly benefit in economic activity, its advantage is in the same industry enterprises can share the specific Labour market, such as internal contact information and industry resources. If the same industry enterprises concentrated in certain areas, to further promote the growth of the industry in this area. From the dynamic perspective, the industrial concentration of external benefit is derived from the regional technology spillover. The technology spillover is advantageous to the local employment, labor productivity and to increase the level of wages.