An adaptive distance protection method is proposed for the problem that photovoltaic (PV) power station side distance protection on the transmission line of PV power station affected by the transition resistance. Comparative analysis is conducted on the different influence principle of transition resistance on the traditional bilateral power lines and the transmission line of PV power station distance protection. A new adaptive distance protection criterion is derived from the geometric relationship of the phase diagram of distance protection measured impedance offset affected by transition resistance and adaptive tuning factor based on the acquisition of additional impedance inclined angle is added in the criterion. The function relation between the inclined angle and the current amplitude ratio and the phase difference between the two sides of the fault line is derived by formula derivation, and a new method of adaptive distance protection for the transmission line of PV power station is proposed. Finally, in DIgSILENT/PowerFactory software, comparative simulation research is conducted on the action situation of distance protection of the PV power station side with different fault types under both traditional distance protection and improved distance protection. The simulation results show that the proposed method can greatly improve the effect of transition resistance on the distance protection of the transmission line of PV power station, and therefore the feasibility of the proposed method is verified.