A linear timing system was designed for the linear injector of Harbin Institution of Technology’s Space Environment Simulation and Research Infrastructure (SESRI) -300 MeV proton and heavy ion accelerator. The linear timing system provides precise timing trigger signals for linear accelerator chopper system with pulse operation mode, low-level RF control system, beam current diagnostic and feedback system to meet the demands of physical beam tuning. The system hardware, based on Field Programmable Gate Array (FPGA), realizes precise timing control of related equipment of linear timing system in internal trigger mode and external trigger mode, as well as the control and safety interlock of chopper. The hardware can realize optical signal communication, W5300 Ethernet communication, multiple relay outputs and multiple synchronized trigger signals with precise timing outputs. At the same time, the use of optical signal communication module will facilitate the cascade of systems and system scalability, which can meet the large-scale needs of linear gas pedal timing system. The user high level software is developed based on the distributed architecture of EPICS (Experimental Physics and Industrial Control System). The linear timing system has been successfully used in SESRI-300 MeV and SSC-LINAC of Institute of Modern Physics (IMP), and has operated stably and reliably for a long period of time without any failure.