Brain tumor image segmentation based on convolutional neural network has become a research hotspot in the field of image processing in recent years. Based on this situation, the significance and research status of brain tumor image segmentation, and the specific advantages of applying convolutional neural network to brain tumor image segmentation are described. Then, the research progress of two-dimensional convolutional neural network, three-dimensional convolutional neural network and the classical improved model of convolutional neural network applied to brain tumor image segmentation is reviewed in detail, and the segmentation results of training in the dataset of multi-mode brain tumor segmentation challenge are summarized. Finally, the future development of convolutional neural networks in magnetic resonance imaging segmentation of brain tumors is discussed.