Abstract: Starting from the perspective of the symbiotic theory of the form population ecology,the paper studies the regional innovation system.It explains the symbiosis theory and proposes that it be a good angle to analyze the RIS-building.According to the elements the symbiotic composed,it analyzes the characteristics of the elements of the regional innovation system in the urban agglomeration-based symbiotic:the symbiotic unit between cities and within cities;the symbiosis model types and the best mode of the development;the symbiotic environment constructed analysis of two ways from the top to the bottom and from the bottom to the top.It describes the evolution of the urban agglomerations symbiotic RIS and analyzes in three ways;horizontal,vertical and mixed.At last it gives some advices of how to build the urban agglomeration-based RIS.