Abstract: By using the high temporal resolution temperature profile data with multi-channel microwave radiometer over the Large High Altitude Air Shower Observatory (LHAASO) from February to May and August to November 2021, combined with the ERA5 reanalysis data in 2021, the Atmospheric Boundary Layer Height (ABLH) with the potential temperature gradient method was calculated and the diurnal, monthly, and seasonal variation characteristics of ABLH were studied. The following findings were obtained: (1) The ABLH showed significant diurnal variation under clear weather conditions. Due to an increase in land surface temperature after sunrise, the ABLH continued to increase, and the maximum height usually appeared in the afternoon, decreased rapidly to the minimum after sunset. (2) Within one year, the average ABLH was the highest in April, about 1200 m, and the lowest in November, only 600 m. The ABLH fluctuated greatly during the daytime and remained stable at night, with an average height of approximately 400 m. The overall result of ABLH inverted by ERA5 was small, but it had the same trend as those from the microwave radiometer. (3) The maximum value of ABLH appeared in spring, followed by summer and autumn, and the minimum in winter. In all seasons, the atmospheric boundary layer height peaked at 14:00 to 15:00.