In order to further improve the efficiency of laser direct writing (LDW) in Cartesian coordinates, the exposure process was proposed to proceed in the accelerating and decelerating sections of the scanning stage, while the exposure effect was guaranteed by the following two ways. The pixel exposure data stored in a line buffer were clocked out by the position feedback pulses during the line scan, driving the acousto-optic modulator to obtain the corresponding beam intensity at the exact desired position. According to the kinetic characteristic of scanning stage, the necessary exposure data under uniform motion and minimum exposure intensity, and exposure data of each pixel in the accelerating and decelerating sections of the scanning stage, are modulated to make the distance of each displacement resolution in it exposed as much dose as that in uniform sections. Numerical simulations indicate that, considering an exposure pattern within a 5 mm × 5 mm area as an example, the total exposure time with the proposed method is 77.77 % of that with exposure only during the scanning stage moving at a constant speed. Meanwhile, the relative error of the exposure dose is increased from 04% to 10% when the bit of the acousto-optic modulator is decreased from 16 to 12.