Improving the information environment to alleviate firm inefficient investment is the key to ensuring the security and stability of the industrial and supply chains. Based on the perspective of shared audit, this paper uses the data of the Chinese Ashare listed firms from 2009 to 2021 to test the effect of sharing audit with customers on firm investment efficiency. The result shows that sharing audit with customers can improve firms investment efficiency, optimizing the information environment and reducing the supplydemand matching costs are the main paths. The crosssectional tests show that the positive effect of sharing audit on investment efficiency is more significant in highly competitive market, high customer concentration and weak supply chain linkages. In addition, gaining renewal opportunities is the motivation for shared auditors to be information intermediaries, and sharing audit not only improves corporate investment efficiency, but also promotes customer value. This conclusion enriches the research on sharing audit enabling supply chain governance, and provides a beneficial reference for suppliers to improve their investment decisions.