The invention discloses a process for manufacturing series of intermediate-voltage N-type vertical conduction double-diffused metal oxide semiconductor (VDMOS) transistors by using composite epitaxy. The process comprises the steps of: batch feeding, first-step epitaxy, second-step epitaxy, third-step epitaxy, fourth-step epitaxy, field oxidation, etching of an active area, high-concentration boron injection and junction depth increasing, phosphorus injection and junction depth increasing, gate oxidation, polycrystalline silicon gate deposition and doping, PWELL boron injection and junction depth increasing, source N+ arsenic injection and junction depth increasing, contact hole etching, aluminum evaporation and corrosion, back thinning evaporation and the like. By a process platform, any additional procedure and operation is avoided, and on-resistance can be lowered by 10 percent on the basis of ensuring withstand voltage; by the VDMOS transistor manufactured by the process, a high-current intense-electric field effect can be effectively suppressed, and the safety working area of a device is enlarged to a certain extent; and the on-resistance is lowered, so that power consumption is greatly reduced, energy sources are saved, and the reliability of a circuit is greatly improved.