In order to improve resisting performance of heat, wear and erosion as well as anti-thermal fatigue, surface build-up welding material of brake-disc for drilling rig with better performance is developed, and its wear mechanism is investigated based on friction and wear experiment at variable temperature. Morphology, constituents and phase structure of wear surface of brake disc are analyzed by employing SEM, EDAX and XRD when thermal equilibrium temperature is at 150°C and 300°C, and its tribological behaviour and wear mechanism of surface build-up welding materials are revealed. In initial stage of wear, friction temperature is lower and hard particles like AL2O3, SiO2, SiC, TiO in brake block plough the surface of brake-disc, oxide layer forms on friction surface with rise of friction temperature and its cracking and regenerating become a major way of wear, meanwhile hard grains in brake block slough off due to frequent ploughing and three-body abrasive wear occurs, and spalling of surface film is mainly caused by fatigue. In stage of high temperature wear, oxidization wear and plastic deformation of brake-disc increase greatly, brake-block starts to soften, severe adhesive wear occurs and spalling of surface film is mainly caused by adhesive tearing. Wear mechanism of brake-disc is comprehensive effects of abrasive, oxidizing and adhesive wear.