Provided are a method, an apparatus and a system for training a neural network, and a storage medium storing instructions. The neural network comprises a first neural network and a second neural network, training of the first neural network has not yet completed and training of the second neural network does not start. The method comprises: obtaining a first output by subjecting a sample image to the current first neural network, and obtaining a second output by subjecting the sample image to the current second neural network; and updating the current first neural network according to a first loss function value, and updating the current second neural network according to a second loss function value. The performance of the second neural network can be improved, and the overall training time of the first neural network and the second neural network can be reduced.