Abstract: This paper aims to analyze the returns to scale of 15 biological institutes in Chinese Academy of Sciences. Firstly, this paper proposed the indicators, including staff, research funding, SCI paper, high-quality paper and graduate training, etc., as the basis for this research. Secondly, this paper uses the methods proposed by Yang to determine directional RTS, optimal inputs direction and congestion effect to investigate the corresponding information of biological institutes. Based on the above analysis, we have the following findings: (1) we can detect the regions with increasing (constant, decreasing) directional returns to scale and the optimal input directions of each institute; (2) we find that directional congestion effect exists in some institutes, and the increase of inputs will cause the decrease of outputs. So these institutes should avoid increasing inputs further and investigate the deep reason for congestion so that the S&T resources can be used more efficiently.

Key words: research institute, returns to scale, directional returns to scale, congestion, directional congestio