Szechuanosaurus campi is a theropod from the Guangyuan City, Sichuan Province, and its horizon is the upper member of the Jurassic Shaximiao Formation. We have observed and analyzed the bone microstructure of bone tissue in the left humerus shaft of Szechuanosaurus campi, the results shows as follows: ① Szechuanosaurus campi has typical skeleton structure of theropod, with inner circumferential lamellae (Endosteum), plexiform vascular canals in laminar fibrolamellar bone tissue,marrow cavity without interstitial lamellae (the trabecular bone), germinal layer of periosteum was dormant. ② In the laminar fibrolamellar bone tissue, every bone plate was thick, and the growth rate of bone was fast; there was a bone reconstruction area in the laminar fibrolamellar bone tissue under the deltopectoral crest, Haversian system was dense, the maximum generation was up to three, and the bone tissue was sensitive to movement and the growth of the deltopectoral crest. ③ There were three LAGs, all of which were shallow, and the individual was 3~5 years old, it was inferred to be in the early phase of stage 2, not reaching its maximum size.