The convolutional neural network (CNN)-based multi-focus image fusion methods which learn the focus map from the source images have greatly enhanced fusion performance compared with the traditional methods. However, these methods have not yet reached a satisfactory fusion result, since the convolution operation pays too much attention on the local region and generating the focus map as a local classification (classify each pixel into focus or de-focus classes) problem. In this article, a global-feature encoding U-Net (GEU-Net) is proposed for multi-focus image fusion. In the proposed GEU-Net, the U-Net network is employed for treating the generation of focus map as a global two-class segmentation task, which segments the focused and defocused regions from a global view. For improving the global feature encoding capabilities of U-Net, the global feature pyramid extraction module (GFPE) and global attention connection upsample module (GACU) are introduced to effectively extract and utilize the global semantic and edge information. The perceptual loss is added to the loss function, and a large-scale dataset is constructed for boosting the performance of GEU-Net. Experimental results show that the proposed GEU-Net can achieve superior fusion performance than some state-of-the-art methods in both human visual quality, objective assessment and network complexity.