In the domain of stereolithography (SLA), laser path planning algorithms are pivotal for optimizing the printing process. Traditional methods, which rely on small or simple variable laser spots, often struggle with balancing printing efficiency and quality, particularly when dealing with models that feature long-narrow or thin-walled sections. This paper introduces a novel path planning algorithm that employs a variable spot size, based on the partition-combination concept. The algorithm consists of following steps: For each layer slice, two sizes of laser spots are used to complete pre-scanning process firstly. Then, the filling region is divided into multiple subregions with different spot types. According to the adjacency relationship, the subregions of the same type are merged into larger ones to ensure the scanning continuity. Finally, the merged subregions are filled and generate scanning paths using variable spot. Experimental results indicate that the proposed algorithm enhances the printing efficiency for models A and B by 19.5% and 21.2%, respectively, over single small spot scanning methods, while maintaining comparable formation quality. Furthermore, when compared to simple variable spot scanning methods, the structural strength of models A and B improves by 14.3% and 14.9%, respectively, with only a minimal reduction in efficiency.