This paper first imports noise trading theory,based on two-tier stochastic frontier model,measures the audit noise,that is uncertainty reflected in audit fees between audit firms and clients;and then discusses its influence on changing audit firm of clients.Taking Shanghai and Shenzhen A shares from 2012 to 2019 as samples,we find that both of the firm and client need to take the audit noise into consideration.The higher the last audit noise,especially higher than the provincial average market noise,the more likely the client is to change the firm in the current period. Among them,84.46% of clients prefer to change to the audit firm that had a pleasant cooperation (no non-standard opinions were issued in the past cooperation).Furthermore,the past pleasant cooperation experience of working with an audit firm can help clients to restrain audit noise.Then,our conclusion is also verified among the clients whose annual reports reveal their reasons for changing audit firm (such as contract expiration, firm resignation, board decision, and others),high abnormal audit fee samples,audit pricing policy liberalization events (2014).Besides, the impact of audit noise is more significant in the sample of non SOEs and non “Big4” clients.This paper observes the client，s choice of an audit firm from the perspective of audit noise,and provides reference for the audit transaction strategy of audit firm and client,and the market supervision of relevant departments.