Based on the first underwater railway shield tunnel,the Shiziyang shield tunnel of Guangzhou Zhujiang River,the prototype test was carried out against its segmental lining structure by using“multi-function shield tunnel structure test system”. And the mechanical characteristics of segmental lining structure using straight assembling and staggered assembling were studied deeply. The results showed that,the mechanical characteristics of segmental lining structure varied with the water pressures;especially after cracking,the high water pressure played a significant role in slowing down the growing inner force and deformation. It also testified that the failure characteristics varied with straight assembling structure and staggered assembling structure.Shear failure often occurred near longitudinal seam when using straight assembling. Based on the first underwater railway shield tunnel, the Shiziyang shield tunnel of Guangzhou Zhujiang River, the prototype test was carried out against its segmental lining structure by using “multi-function shield tunnel structure test system”. And the mechanical characteristics of segmental lining structure using straight assembling and staggered assembling were studied deeply. The results showed that, the mechanical characteristics of segmental lining structure varied with the water pressures; especially after cracking, the high water pressure played a significant role in slowing down the growing inner force and deformation. It also testified that the failure characteristics varied with straight assembling structure and staggered assembling structure. helar failure very experienced near longitudinal seam when using straight assembling.