Abstract: Taking the relative panel data of A share companies, excluding the special treated and the financial industries, listed in both Shanghai and Shenzhen stock exchanges from 2003 to 2013, whose state-owned shareholding proportion is more than zero, as samples, this paper conducts an empirical study with panel threshold regression. The results show that the mixed ownership companies with state-owned shares but not controlled by them have such an optimal range of state-owned shareholding proportion as（5.01%，15.46%）, the state-owned shareholding proportion is approaching 15.46%; the mixed ownership companies relatively controlled by state-owned stocks have such an optimal range of state-owned shareholding proportion as（32.16%，43.86%）, the state-owned shareholding proportion is approaching 32.16%; the mixed ownership companies absolutely controlled by state-owned stocks have such an optimal range of state-owned shareholding proportion as（74.56%，100%）.

Key words: state-owned shareholding proportion; optimal range; panel threshold regression