The work aims to improve wear resistance of 35CrMo steel used for drilling pipe joints and casing pipes. The 35CrMo steel was first pre-treated by ultrasonic surface processing and then by sulfonitriding treatment to study effects of surface pre-treatment and lubrication conditions on corrosion resistance of the steel. Surface morphology, roughness, composition and phase structure were characterized by optical profilometer, scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). The wear resistance of 35CrMo drilling pipe joints subject to ultrasonic surface pretreatment at different loads as well as casing pipes were evaluated by a ring-block wear tester with and without lubrication of oil-based drilling fluid respectively. The ultrasonic surface processing could remarkably reduce the surface roughness of both 35CrMo substrate and the samples with sulfonitriding treatment by over 80%. Sulfonitriding samples pre-treated by ultrasonic surface processing could obviously improve the wear resistance of 35CrMo steel with and without lubrication of oil-based drilling fluid. The ultrasonic surface processing under load of 500 N showed more obvious improvement in the wear resistance without lubrication of drilling fluid with the decrease of adhesion and furrows. Pretreating 35CrMo steel by ultrasonic surface processing and sulfonitriding treatment can obtain lower surface roughness and higher surface micro-hardness, and improve the wear resistance of both 35CrMo drilling pipe joints and casing pipe with and without lubrication of drilling fluid.