Due to their characteristics of high frequency, low noise, low power consumption, and high gain, InP-based High Electron Mobility Transistors (HEMTs) show great potential in space high-frequency signal receiving systems. To enhance the application of InP-based HEMTs in space radiation environments, a study was conducted using two-dimensional simulations to investigate the effects of particle incidence position, temperature, and incidence angle on single event transients (SETs) in InP-based HEMTs. The results indicate that different incident locations have varying impacts on peak drain current and collected charge, with the gate position exhibiting the highest sensitivity to SETs, resulting in the largest peak drain current and collected charge. As the incident angle increases, more holes are generated in the buffer layer, leading to a reduction in the potential barrier under the gate, which in turn increases both the peak drain current and pulse width. Conversely, an increase in temperature leads to a decrease in electron mobility within the channel, reducing both peak drain current and pulse width. When considering the combined effects of temperature and particle incidence angle, it is evident that temperature significantly influences the peak drain current generated by small-angle incidence. This research provides a theoretical foundation and practical guidance for designing InP-based HEMTs that are resilient to SETs in space applications.