The invention provides a roof garden combination planting module which does not need water, electricity, artificial watering and maintenance and is energy saving and environment friendly. The module consists of five parts of a rain water collecting box, a drainage plate, a planting box, edge sealing strips and angle sealing strips. The module is particularly applied to the greening of old houses and light steel roofs, which is low in cost requirement, small in bearing and difficult in watering and maintenance. The combination planting module depends on the structural advantages and has the characteristics of plant root resistance and water storage intercommunication; on the one hand, the module can be directly arranged on roofs to be used without needing the cooperation of root resistance waterproof coiled materials of other plants, on the other hand, the module does not need a large number of water supply pipes and adaptors, thereby greatly reducing cost of a roof garden system. Depending on the advantages of the standardized function design, the combination planting module has the characteristics of high commonality of products, strong adaptability of the system, high survival ratio of plants, short construction cycle, no construction rubbish, quick and convenient arrangement, low labor intensity, low product cost and convenient large-scale flow line production, etc.