1. Take a sample from the training set and input the information data of the sample into the network.<br>2. The actual output of the neural network is obtained after the connection between the nodes is processed layer by layer.<br>3. Calculate the error value between the actual output and the expected output of the network.<br>4. The error is transmitted back to the previous layers layer by layer, and the error signal is loaded on the connection weight according to certain principles, so that the connection weight of the whole neural network is transformed to the direction of error reduction.<br>5、 Repeat the above steps for each input-output sample in the training set until the error of the whole training sample set is reduced to meet the requirements.<br>