The present invention discloses a photovoltaic power generation-based railway traction power supply system. The photovoltaic power generation-based railway traction power supply system comprises a photovoltaic power generation device, a photovoltaic inverter, a step-up transformer, a traction transformer and a traction power supply system; the electric energy output end of the photovoltaic power generation device is connected with the primary side port of the step-up transformer through the photovoltaic inverter; the secondary side port of the step-up transformer is connected with the traction power supply system; the traction power supply system is connected with the traction transformer connected to a power grid transmission line; and a V/V wiring type step-up transformer is adopted as the step-up transformer. According to the photovoltaic power generation-based railway traction power supply system of the present invention, a self-power generation, self-use and redundant electricity marketing power generation mode is adopted, and therefore, the normal operation of the traction power supply system can be ensured, and redundant electricity is consumed by a power grid. The photovoltaic power generation-based railway traction power supply system is simple in structure and low in investment cost.