The truss type steel composite support has the advantages of green, high efficiency and micro-deformation control, and has been widely used in deep foundation pit engineering under complex environment. However, the truss type structural system is limited by the on-site assembly process, and there are problems such as dense node structure and assembly deviation. Under the coupling effect of temperature effect, the mechanical behavior of the support system changes more complex and intense, which constitutes the potential instability risk of the foundation pit. The deep foundation pit project of a hospital in Jinan was taken as the research object. Through the joint monitoring test of temperature field and axial force, the influence of day and night temperature change, seasonal temperature difference and weather change on the mechanical behavior of supporting structure was systematically studied. It is shown by the results that the axial force of the support rod was caused to fluctuate periodically by diurnal temperature change. The redistribution of the axial force is led to by seasonal and weather changes, resulting in a sharp increase or loss of the axial force of the local rod, and the redistribution of the axial force is mainly caused by solar radiation. Based on this, a control method to reduce the temperature effect by shielding solar radiation was proposed. It is demonstrated by experimental verification that this measure can significantly optimize the axial force distribution mode of the support system and improve the overall stability of the foundation pit.