Image colorization aims to convert grayscale images into color images, a technique that has long received extensive attention from researchers in the fields of computer graphics and computer vision. It has found wide applications in areas such as image restoration, medical imaging, film restoration, and artistic creation. Over decades of development, researchers have proposed a large number of interaction-based, rule-based, and deep learning-based algorithms to enhance the colorization effect of images. Nevertheless, the existing image colorization algorithms exhibit some significant shortcomings, such as low computational efficiency, cumbersome user interaction, low color saturation, and the occurrence of color overflow. To address these challenges, an image colorization algorithm based on semantic similarity propagation was proposed. Semantic features of the input grayscale image were extracted using deep neural networks, and a feature space was constructed. Then, the image colorization task was formalized as an efficient energy optimization problem based on semantic similarity propagation, enabling the propagation of user-supplied stroke colors to other regions of the image. In addition, a trilinear interpolation method was employed to accelerate both energy optimization and color propagation, significantly enhancing computational efficiency. In order to verify the effectiveness of the algorithm, experiments were conducted on a collected image set, evaluating multiple dimensions, such as image visual effect, generated image quality, algorithm running time, and user interaction experience. The results of a large number of qualitative and quantitative experiments demonstrated that the proposed algorithm achieved more accurate, efficient, and natural colorization with reduced user interaction requirements, while achieving substantial improvements in computational efficiency.