Based on the heuristic packing algorithm, this paper proposes a 3D packing algorithm that can run efficiently to improve the efficiency of palletizing and packing. The design of the algorithm starts from three parts: block construction, remaining space processing, and optimal block search. Firstly, the goods are packed to meet the constraints of the direction of the goods and the constraints of the support of the goods, and various composite blocks are generated. Then, set the remaining space selection, division, and merging methods that meet the priority constraint rules. Then, a sliding window and integer-split heuristic search are used to select the optimal block for each generated space. Finally, the feasibility of the algorithm is proved by experiments.