Taking Chinese listed companies and their signature auditors from 2012 to 2016 as samples， the threshold regression model is introduced to empirically analyze how auditor’s personal workload pressure affects audit behavior and decision making and earnings quality under the support of different organizational mechanisms of firms. The results show that：The threshold effect exists in the industry expertise of accounting firms. The higher the level of industry expertise， the greater the firm’s organizational support， and the smaller the negative impact of auditor workload pressure on the earnings quality of a company. The threshold effect also exists in the comprehensive evaluation of accounting firms. The lower the level of comprehensive evaluation of accounting firms， the less the firm’s organizational support， and the greater the negative impact of auditor workload pressure on the earnings quality of a company. In addition ，the threshold effect exists in the human capital of accounting firms. The higher the level of human capital， the higher the auditor’s work efficiency， the less the negative impact of auditor workload on the earnings quality of a company.