Proximity effect is an important factor which limits optical lithography resolution, and it also limits the applications of laser direct writing system in submicron and half-submicron optical lithography. The production mechanism of proximity effect in laser direct writing is analyzed, its differences with projection optical lithography and electron beam lithography pointed out, and a convenient and effective optical proximity correction (OPC) method presented. The experimental results show that the feature size of 0.6 micron can be got by using OPC method in ISI-2802 laser direct write system.