Abstract: Based on the data of teams in China Football Association Super League in season 2009—2015,this paper constructs panel data in which treatment groups and control groups are matched,and studies the causal relationship between within-season coach turnover and teams performance by matching difference-in-difference method.It draws conclusions as follow:firstly,coach turnover significantly improve teams' short-term performance.Specifically,the points gain per game and winning probability in turnovered teams are 0.27 and 8.7%higher than the ones in unturnovered teams.However,goals or concedes per game of teams do not change with coach turnover events.Secondly,the individual characteristics of new coaches have no significant impact on the effects of coach turnover.Therefore,coach turnover improve teams performance by the mechanism of triggering competition between players within-team.