The atmospheric boundary layer (ABL) and its variation in coastal regions are of great significance for weather forecast and wind energy. Nevertheless, the influence of onshore winds on the ABL height (ABLH) remain poorly understood, largely due to the scarcity of observations. Here, for the first time, we retrieved the daytime ABLH and turbulence dissipation rate (ε) using one-year (2022) worth of wind profiling measurements from eight radar wind profile stations along the southeast coast of China. Afterwards, the spatial and temporal variability of ABLH were investigated, with a focus on the effect of onshore winds on the ABLH. The ABLH follows the same semi-diurnal variation pattern as that of ε. Moreover, the mean ABLH during summer (winter) onshore wind periods is decreases (increases) with the increase of onshore wind intensity. This indicates that the influence of onshore winds on ABLH varies seasonally. In summer, the onshore winds bring the cold marine air masses to the warm land surface, which lowers the temperature inside the ABL and reduces turbulence intensity, thereby suppressing the development of ABLH. By contrast, in winter, the onshore winds caused by temperature difference increase the level of vertical wind shear within the ABL, which enhances the turbulence intensity, thus promoting the development of ABLH. The findings obtained here are useful for understanding the variations of ABLH under different wind conditions in coastal areas.