Abstract: A processing device for executing convolution neural network computation and an operation method thereof are provided. The convolution neural network computation includes a plurality of convolutional layers. The processing device includes an internal memory and a computing circuit. The computing circuit executes convolution computation of each convolutional layer. The internal memory obtains weight data of a first convolutional layer from an external memory, and the computing circuit uses the weight data of the first convolutional layer to execute the convolution computation of the first convolutional layer. During a period when the computing circuit is executing the convolution computation of the first convolutional layer, the internal memory obtains weight data of a second convolutional layer from the external memory, so as to overwrite the weight data of the first convolutional layer with the weight data of the second convolutional layer.