CNC WEDM technology has been widely used in China. According to general principles of software engineering, the software system of double wire-electrode cutting simulation machining based on 3B code is designed for these cutting machines by adoption of the waterfall exploitation model. This system is completed with the functions of the 3B code analysis, simulation of cutting, processing and management, user management, and software activation. After plenty testing, the system has high parsing speed, high precision machining simulation, and it also has a certain value. This paper gives a detailed description of the design scheme, gives a comprehensive discussion on the key technologies, such as 3B code analysis, synchronous point setting and synchronous simulation cutting, and also has certain references for the realization of upper computer control software for wire-electrode cutting system.