Abstract: The welding cold crack sensitivity of 50 mm thick EH36-Z35 marine engineering steel in a low temperature environment was studied by empirical formula and inclined Y-groove welding crack tests. The results show that the test steel had a certain welding cold crack sensitivity, and the safety of the structure could be guaranteed only when the preheating temperature before welding was about 114 ℃, according to the calculation by the empirical formula. The preheating temperature before welding should be higher than 125 ℃ at environmental temperature of 15 ℃ and should be higher than 150 ℃ at environmental temperature of 5 ℃, according to the inclined Y-groove welding crack tests. The test results were close to the theoretical calculated values. At environmental temperatures of -18 ℃ to 15 ℃ and with similar absolute humidity and same preheating temperature, the crack rate at the weld root of the test steel increased, and the maximum hardness of the heat-affected zone increased with decreasing environmental temperature. The maximam calculated critical constraint stress was 577 MPa at environmental temperatures of -18 ℃ to 15 ℃, and the constraint stress introduced by inclined Y-groove welding crack tests was 588-1 695 MPa, which satisfied the condition of crack formation and led to crack generation and propagation.