In this paper, the Am-241 is used as an alpha particle radioactive source to investigate the soft error mechanism in 65-nm and 90-nm static random accessmemory (SRAM). Combining reverse analysis, TRIM and CREME-MC Monte Carlo simulation, the energy transport process, deposited energy spectrum and cross-section characteristics of alpha particles in the device are revealed. The results show that the soft error sensitivity of the 65-nm device is much higher than that of the 90-nm device, and no flipping polarity is found. According to the real-time measured soft error rate at an altitude of 4300 m in Tibetan Yangbajing area, the thermal neutron sensitivity and alpha particle soft error rate, the overall soft error rate of 65-nm SRAM used at sea level of Beijing city is 429 FIT/Mb, and the contribution from alpha particles is 70.63%. Based on the results of reverse analysis, a three-dimensional simulation model of the device is constructed to study the influence of the incident angle of alpha particles on the single event upset characteristics. It is found that the corresponding deposition energy value at the peak of the number of particles in the sensitive region decreases by 40% with the incident angle increasing from 0° to 60°. While the single event upset cross sectionincreases by 79% due to the apparent single event upset edge effect in a sensitive region of the 65-nm device.