An automatic fare collection system for temporary parking lots based on plate number recognition is proposed to resolve parking difficulty and enhance the operation efficiency of the parking lots in densely populated areas. First, cameras at the entrance will take snapshots of vehicles. Subsequently, the system will identify, adjust and split license plate characters with image processing techniques, and then recognize the specific characters through a convolutional neural network. After that, in-out time, duration, and fare will be recorded and calculated in the MySQL database. Finally, an operation dashboard is designed to visualize and manage the system. The whole system is simulated by OpenCV and C++, and results prove a recognition rate of 97% or above. The device is portable with highly automatic operation, greatly facilitating the management of temporary parking lots.