This paper divides the annual report pressure of signature CPA into that of workload, time, client disclosure and regulatory enquiry from the perspective of “task-based pressure source and social pressure source”,based on the data of A-share listed companies in China from 2014 to 2019, and examines the influence of them on the choice of audit opinion type.The research shows that when the signature CPAs face pressure of workload,time and clients’ requirement to disclose the annual report in advance, they tend to issue standard opinions. The more the audit clients contracted by signature CPAs were inquired by supervision in the previous year,the more likely they are to issue non-standard audit opinions. Additional tests show that this effect is more significant for the project partners. This paper provides some reference and inspiration for accounting firms to arrange CPAs reasonably during the period of annual report.