An R-type thread belongs to the field of fasteners. Both lateral sides of a thread tooth form are a first lead-in side angle line (101) and a second lead-in side angle line (102) respectively. The first lead-in side angle line and the second lead-in side angle line are connected through a transition line (103). The transition line is concaved in a direction away from a crest. The present technical solution overcomes the defect of the existing threads of being easy to get loose after assembled, providing the R-type thread which has the functions of resisting vibration and looseness.