This study investigates the impact of the controlling shareholders equity pledge on enterprises inefficient investment, using the annual observation data of Chinas AShare listed companies from 2007 to 2019. We find that: the controlling shareholders equity pledge will increase the firms inefficient investment; there is a significant nonlinear double threshold effect of the controlling shareholders shareholding ratio on equity pledge and the enterprises inefficient investment. We use the Panel Threshold Regression Model to analyze the threshold effect and find that with the increasing of the shareholding ratio of controlling shareholders, the relationship between equity pledge and inefficiency investment will be strengthened first, then weakened and finally enhanced; enterprises internal control quality play a positive regulation role on the relationship between the controlling shareholders equity pledge and the enterprises inefficient investment. This study reveals the economic consequences of the controlling shareholders equity pledge on the enterprises investment efficiency and enriches the research on equity pledge and enterprise investment efficiency.