Abstract: Xylocopa tranquebarorum belongs to the tribe Xylocopa within the subgenus Biluna(Hymenoptera: Apidae), usually nests in the dead bamboo. In this paper nest entrance size of X. trannquebarorum, thickness of bamboo cortex and the diameter of bamboo gnarl of Bambusa multiplex were measured with vernier caliper. The results showed that nest entrance of X. trannquebarorum were elliptical-shaped, 5-11.5 mm length(mean and SD: 6.5±0.63 mm, n=1975)and 5-9.5 mm width(mean and SD: 6.8±0.52 mm, n=1975). Among them, the highest selection rate was 6.50 mm in length and 6.99 mm in width, accounting for 43.70% and 42.33% of total nest entrances, respectively. The diameter and thickness of nest entrance of X. trannquebarorum were about 19.43(±2.33)mm and 3.1(±0.74)mm,respectively. Among them, the favorite bamboo diameter and thickness of bamboo cortex were 17-21 mm(59.01%)and 2.5-3.5 mm(69.16%)in Bambusa multiplex. Significant variation was found in its nest entrance size,thickness of bamboo cortex and the diameter of bamboo gnarl of the Bambusa multiplex culm.