The invention discloses a multispectral remote sensing image fusion method and a multispectral remote sensing image fusion device based on residual learning. The method comprises the following steps:(1) acquiring a plurality of original multispectral remote sensing images IMS and corresponding original panchromatic band remote sensing images IPAN; (2) calculating to obtain an interpolation imageIMSI of the IMS, a gradient image GPAN of the IPAN and a differential image DPAN; (3) constructing a convolutional neural network fusion model which comprises a feature extraction layer, a nonlinear mapping layer, a residual image reconstruction layer and an output layer which are connected in sequence, taking I=[IMSI,IPAN,GPAN,DPAN] as input for training, and taking a loss function adopted duringtraining as a mean square error function for introducing residual learning; and (4) processing the multispectral remote sensing image I'MSRI to be fused and the corresponding original panchromatic band remote sensing image I'PAN to obtain corresponding data [I'MSI, I'PAN, G'PAN, D'PAN], inputting the data into the trained convolutional neural network fusion model, and outputting an image after fusion. The method is high in fusion speed, and the spectrum and space quality of the fused image is higher.