In order to solve the problems such as traditional tedious calculation work and heavy workload in the design of plain steel gate, the basic gate design theory and method of plane structure system were chosen in the paper. Based on VB6.0, a simple and practical design platform was developed, in which modern compute technology such as database, graphics processing, document generation and computing simulation tool were applied. This design platform included design, calculation, drawings and design manual. Finally,the paper respectively used the gate design platform and the traditional design methods to calculate the design parameters of an engineering example, then compared the former design parameters and the later ones. The results show that the gate design platform meets the requirement of project.