Abstract: Low gain avalanche detector (LGAD) is a new type of semiconductor detector with the advantages of small channel area and high time precision. It has been selected for the upgrade project of the large particle spectrometer ATLAS on LHC (Large Hadron Collider). To fully leverage the intrinsic benefits of LGADs, a dedicated multi-channel readout electronics system with high timing precision is essential. In response to this requirement, the ATLAS Collaboration has developed the ALTIROC (ATLAS LGAD Timing Integrated ReadOut Chip) series of application-specific integrated circuits (ASICs).This work presents a scalable, multi-channel, high-precision readout system design for LGADs based on the second-generation ASIC—ALTIROC2, and the performance of this system was performed. The test results show that the time measurement precision of the LGAD readout electronics system based on ALTIROC2 ASIC is better than 25 ps, and a data rate of 400 Mbps is achieved, satisfying the data throughput requirements under high event rates.