The method of cultivating mangrove in tidal zone adopts bamboo tube fixing technology. Bamboo tube is formed through breaking the bamboo nodes while leaving part of the lowest one for fixing the root of mangrove seedling, forming wedge in the lower section for being inserted into soil, and forming small side crack. Soil and mangrove seedling are then set inside the bamboo tube for artificially cultivation, and the bamboo tube with survived mangrove seedling is inserted in tidal zone, where the mangrove seedling grows further first inside the bamboo tube and then in the mud land after the bamboo tube is broken gradually. The bamboo tube serves as the nutritious pot for fixing and protecting mangrove seedling.