Embodiments of the invention provide image classification neural network model building and image classification methods and devices. The image classification neural network model building method comprises the steps of firstly, acquiring a training set containing classified images; according to the distance between convolutional layers in dense blocks of a densely connected convolutional neural network model, determining the number of characteristic diagrams of the convolutional layers in the input dense blocks; forming a second densely connected convolutional neural network model; training the second densely connected convolutional neural network model by using the training set to generate an image classification neural network model; and classifying to-be-classified image data by using the image classification neural network model. According to the image classification neural network model building and image classification methods and devices, network parameters in an image classification process are reduced.