Aiming at the single-phase grounding short-circuit fault of photovoltaic grid-connected station based on positive-sequence control, this paper studies internal faults and external faults of photovoltaic plant respectively and proposes their adaptive fault location algorithms. For the external fault of the photovoltaic plant, this method only uses the electrical information of the opposite end system of the photovoltaic plant to get the analytical expression of the fault distance, which is not affected by the impedance change of the opposite end system. For the internal faults on the collector line of a photovoltaic plant, it uses the electrical information of the systems at both ends to obtain an analytical expression of the fault distance. The method has the advantage of no false roots and no need to search and iterate, and the calculation amount is small and the robustness is strong. The simulation results of MATLAB show that the proposed method can effectively locate the fault point in the two cases of external and internal faults of the PV power plant, is not affected by the transition resistance, and the ranging accuracy is high. This work is supported by National Natural Science Foundation of China (No. 51577018).