To investigate the influence of temperature effect on the measurement accuracy of hydrostatic leveling system ( HLS) and reduce the measurement error, a temperature gradient test platform is established, which combines with the ambient temperature research completed in the previous stage. Researches are conducted on the HLS measurement accuracy under temperature gradient conditions, and the heating / cooling mode, temperature gradient TG variation, liquid expansion coefficient γdi and communicating pipe expansion coefficient γpi, and measuring-point distance Dtest are analyzed quantitatively. Results show that the temperature gradient influence coefficient ΔPt-G between the heating and cooling mode is only 0. 003 mm/ ℃ , which indicates the limited effect of the heating / cooling mode on the HLS measurement accuracy. The elevation of the measuring point has an obvious correlation with TG . The ΔPt-G has a linear correlation with the (γdi - γpi) and also shows the power function relationship with Dtest . Finally, a modified model for the temperature effect-induced error in HLS is formulated. The reliability and applicability of the model are evaluated by the settlement tests of the Nanjing Yangtze River tunnel and Taihu tunnel.