As a measurement tool of wind speed environmental noise, surface microphone is widely used in aerospace and vehicle fields. It is a flat structure and has no cavity in the front end, so it can only be calibrated by conventional means. In this paper, a kind of surface microphone calibration technology is studied. The methods of a flat asymmetric short coupling cavity and a large diameter flat surface microphone mounting gland are adopted. Through simulation analysis and test verification, the surface microphone can be calibrated effectively.