In the background of mixed ownership reform in state-owned enterprises,this paper tests the differences in firm innovation behavior before and after the privatization of micro innovation subjects from the perspective of innovation efficiency.It finds that privatization curbs firm innovation efficiency and the number of patents owned by firms significantly reduces; and this effect is more significant in listed companies that lack original state-owned blockholders counterbalance&are not the family enterprises after the privatization and regions with weaker external property protection,and compared with entrepreneurship firms,privatized firms have lower innovation efficiency.Further study shows that an important route to the inhibition of firm innovation efficiency by privatization lies in that related exchanges obviously increase,investment significantly reduces,and after privatization,non-state-owned large shareholders mostly have the motivations for tunneling&decrease innovation practice,thereby leading to the reduction in innovation efficiency.The conclusions provide a new perspective for the understanding of the efficiency of privatized enterprises,help to correctly recognize and understand the privatization behavior of emerging transition economies,and have critical policy implications for how to advance mixed ownership reform by regulation authorities.