The large -diameter shield tunnel is usually designed to be many segment blocks and the ratio of thickness to diameter is smaller. A similar model test is conducted to study the influence of segment thickness on the force and deformation of a large-diameter shield tunnel. The results show that, increasing the thickness of segments can effectively reduce the convergent deformation of the tunnel under overload condition, whilesuch ef- fect will gradually decline with the increaseof segment thickness. The increase of segment thickness can alleviate the problem of concrete cracking at the arch roof and bottom, but the stress state of tunnel section will be changed into large eccentric from small eccentric. And too large segment thickness is not conductive to bearing capacity for the tunnel structure. The growth of the segment thickness has the most obvious effect on the internal force of the arch waists, followed by the arch roof and arch bottom of the tunnel, and there is no significant in- fluence of internal force on other parts of the tunnel.