Abstract: Currently, the main method used for the technical efficiency evaluations of research institutes in China is DEA, which is limited to cross-sectional comparison without the time trend for evaluation units. In order to remedy the defect of DEA, the method of Stochastic Frontier Analysis(SFA) based on Cobb-Douglas production function is applied to evaluate the efficiencies of 82 institutes in CAS during the period of 2004-2007. The results show that the overall efficiency presents a decline trend. Key words: Cobb-Douglas production function; technical efficiency; SFA; maximum likelihood estimation