Abstract: The welding thermal simulation test was conducted on medium thick Q960 steel plate for hydraulic supports. The microstructure and hardness of the coarse-grained heat-affected zone under different cooling rates (0.5-100℃·s^-1) were analyzed. The robot welding process was determined by Tekken test and welded joint mechanical performance tests. The results show that the simulated hardness of coarse-grained heat-affected zone could be stabilized below 420 HV when the cooling rate was lower than 80℃·s^-1, namely the welding heat input was greater than 6.5 kJ·cm^-1 under the preheated temperature of 100℃. The Q960 steel plate joint welded by robot welding had excellent cold crack resistance sensitivity under the welding heat input of 13.95 kJ·cm^-1 and the preheated temperature of 100℃. The properties of robot welding Q960 steel plate joint could meet the standard requirements within the welding heat input of 13.02-15.18 kJ·cm^-1 with ER96-G welding wire. The recommended welding parameters for robot welding were listed as follows:preheating at 100℃, welding current of 460 A, voltage of 33 V, welding speed of 60 cm·min^-1 and wire feed rate of 8.5 m·min^-1, and the welding deposition rate could reach 8 kg·h^-1.