The digital satellite mainly simulates the satellite’s central management unit (CMU), control subsystem, chemical propulsion subsystem, electric propulsion subsystem, orbit and attitude dynamics, avionic subsystem, measurement and control interface, the communication between CMU and avionic subsystem is realized by simulating 1553B bus interface. In this paper, based on the fully-configured satellite of Dongfanghong-4 enhanced platform, a new generalized digital satellite based on software-in-the-loop is presented. The modularized design and integration of the common parts and the configurable design of the different parts are adopted to improve the versatility and maintainability, at the same time, the simulation of the CMU hardware structure is realized, and the on-board software can be embedded without modification. It has been successfully applied to high-orbit satellites for the first time, greatly improving the efficiency, reliability and in-orbit application.