In order to solve the problem of high-precision surface shape detection of Φ2 m plane mirror and improve the reliability of the Ricky-Common detection method, a Φ2 m plane mirror surface shape detection technology based on unit excitation method and inverse complex calculation was studied. The influence of error sources such as airflow disturbance and spherical mirror surface shape on the calculation method of unit excitation surface shape was analyzed. The combination of unit excitation and optical software inverse complex calculation was used to improve the reliability of the Ricky-Commonn detection method. The effect of airflow change on surface shape recovery during the detection of Φ2 m plane mirror was simulated and analyzed. The results show that under the influence of airflow, the stability of surface shape calculation remains at 0.003λ after multiple average calculations. The surface shape calculation the accuracy reaches 0.0079λ under the influence of spherical mirror shape. Using this method, the surface shape processing process of the actual Φ2 m plane mirror was controlled, and the surface shape detection results showed that the RMS of the plane mirror reached 0.0415λ, and the PV was 0.2040λ (λ=632.8 nm). The purpose of this research is to solve the problem of shape detection of large-diameter plane mirrors under the influence of errors, which has important application significance for actual mirror processing and detection.