Abstract: The new generation of space environment monitor (SEM), SEM-II, onboard the Chinese meteorological satellite, FengYun-3E, has the abilities to measure the charged particles flux with the particle energy from 30 eV to 300 MeV in multi-directions, the satellite surface potential, the radiation dose in sensors, and the geomagnetic field variations. The space environment detections derived from SEM-II can be utilized for satellite security designs, scientific studies, development of radiation belt models, and space weather event monitoring or disaster warning. In this paper, we introduce the SEM-II’s instrument characteristics, interpret the in-orbit calibration algorithm, perform the quantitative test to check the particle and the magnetic field detections’ accuracies by the cross-calibration methods, and do the qualitative test to check if the radiation dose and the surface potential detections follow the nature law of space environment by comparing with the historical records. The instruments’ responses to the space weather events are also presented.