The invention discloses a photovoltaic maximum power tracing system and method based on P-U curvature characteristics. The method includes the following steps: sampling the output voltage and the output current of a photovoltaic cell panel in real time; calculating curvature changes corresponding to P-U curves output by the photovoltaic cell panel in real time; determining the duty ratio change direction of a Boost circuit in the next step according to the direction of the curvature changes and the direction of changes of the voltage output by the photovoltaic cell panel; sending the adjusted duty ratio to the Boost circuit to control the output voltage of the photovoltaic cell panel to be adjusted in the maximum power output direction. By means of the photovoltaic maximum power tracing system and method, the tracing direction is determined with the method of calculating the curvature increments of the P-U curves output by the photovoltaic cell panel in real time, maximum power point tracing of a photovoltaic cell is achieved, the response speed is high, rapid tracing control is easily achieved, and the photovoltaic maximum power tracing system and method are suitable for areas with the high external environmental change speeds; in addition, shocks nearby the maximum power point are small, and power losses nearby the maximum power point are fewer.