The image super-resolution (SR) operation holds multiple solutions with the one-to-many mapping from low-resolution (LR) to high-resolution (HR) space. However, the SR of different scales for the same image is usually regarded as independent tasks in the existing SR networks. Therefore, these networks are inflexible to effectively utilize feature learning experience and require much more computing time to recover HR images in higher resolutions. Recent arbitrary scale SR methods still cannot solve these problems. To efficiently and effectively recover HR images, this paper presents an efficient multi-scale learning method for image SR networks based on a novel self-generating (SG) mechanism. This method (briefly named SG-SR) utilizes the feature learning results of SR networks to generate upscale filters by using the novel SG upscale module, which is proposed to replace the traditional upscale module. For each scale factor, the SG upscale module provides the corresponding amount of the spatial weights to filter the LR tensor and then converts filtered tensors with the original tensor to corresponding HR images. The proposed method is evaluated through extensive experiments and compared with state-of-the-art (SOTA) methods on widely used benchmark datasets. The experimental results show that our method has superior performance compared with SOTA methods, and the SG upscale module can improve the performance of existing SR networks effectively. What is more, our module has a much less calculation cost than the other upscale modules.