Laser interference direct writing device constructed with MEMS (microelectro mechanical systems) micromirrors has advantages such as small size, fast writing speed and simple optical path. However, it is necessary to adjust the exposure time to achieve uniform exposure effect during scanning. We introduce the optical path composition and control method of this type of laser interference direct writing device. The lookup table method is used to optimize the generated exposure pattern and exposure time parameters, reducing the pixel diameter variation from about 84% to about 6%. It solves the problem of uneven exposure time in the application of laser interference direct writing devices based on MEMS micromirrors.