Based on the data of drilling，logging and seismic and the basin modeling technique，the effects of salt on thermal evolution of source rock and the reservoir temperature were studied taking Block X in Gabon coastal basin as an instance. The results indicate that the distribution of salt is in ribbon pattern or in dot scope in the study area，and the thickness of salt is between 0 and 3 723 m with an average of 808.5 m. The thermal conductivity of salt is typically two or three times larger than that of other sedimentary rock. Therefore，under constraint of the high thermal conductivity of salt，the source rock maturity of the Madielais Formation is risen，and the source rock maturity of the Melania Formation is reduced，and the reservoir temperature of the Dentale Formation is reduced. The thicker the layer of salt is，and the nearer the layer of salt is to the formations，the larger the effect of salt on vitrinite reflectance is. To the isobathic layer under the salt，the difference between Ro with effect of salt and without effect of salt is 0.6% when the Ezanga stratum thickness is 2.0 km，and the difference between Ro with effect of salt and without effect of salt is only 0.1% when the Ezanga stratum thickness is 0.2 km. Ro difference of the Vembo Formation nearer salt may be more than 1.2%，and that of the Melania Formation which is farther away from the salt may be less than 1.2%. The thicker the salt is，the greater the influence of salt on reservoir top and bottom temperature is. Temperature difference between reservoir top and bottom are 30.66 and 29.22 ℃ respectively when the Ezanga Formation thickness is 2.0 km，and those values drop to 5.06 and 3.14 ℃ respectively when the Ezanga Formation thickness is 0.2 km. Therefore，hydrocarbon source rock thermal evolution and reservoir temperature are affect?ed by the thickness of the salt body，shape change，etc.，Ro revealed by drilling data cannot be used simply to predict Ro of the source rock around and its thermal evolution in salt zone.