Abstract: In order to collect the pressure change in the process of aluminum alloy spot welding, realize real-time monitoring of nugget state and improve the quality of welding joint, a filter system for pressure acquisition of aluminum alloy spot welding was designed.The first step, the acquisition circuit was designed to realize the real-time acquisition and level conversion of pressure signal; the second step, based on the analysis of the interference source of pressure signal, the method combining hardware filtering and software filtering was designed to solve the problem of pressure signal interference.The experiment results show that the pressure waveform obtained by the system changes smoothly and can accurately reflect the pressure change and nugget state in the welding process.After the use of the system, the average nugget diameter of the solder joint is increased by 10%, and the solder joint has no cracks and fewer pores.