In order to make better use of solar energy, automatic tracking system is more and more used in solar energy industry. The solar panel automatic tracking system based on programmable logic controller (PLD) includes hardware and software, in which the hardware includes PLD input and output port, signal processing unit and driving part; The software includes PLD control and monitoring program. The solar panel automatic tracking system enables the photovoltaic panel to track the solar care in real time, so as to obtain solar energy to the greatest extent, effectively improve the utilization rate of solar energy and the efficiency of photovoltaic power generation system, and reduce the cost of photovoltaic grid connected power generation. It has theoretical research significance and application promotion value.