Abstract: For continued construction of the existing steel structure，it is necessary to transform and reinforce the built parts thus，making up the loss of the original structural properties． Load reinforcement technology was used to reinforce steel columns of the original structure，the intermittent mode was used to weld steel columns，reduce the damage on the original loading structure，and reduce the amount of welding，save construction investment． Through laboratory scaled tests of loaded steel columns under different reinforcement welding forms， the measured data of the carrying capacity of reinforced steel columns under different reinforcement welding forms were got． Combined with digital simulation and laboratory test data，the raising ratio of the carrying capacity of the reinforced steel columns after reinforcing the original structure was determined． The effect of reinforcing and welding process on the loaded steel columns was also studied． Digital simulation analysis techniques were used to analyze the stress distribution， deformation and recovery of steel beams and braces after the completion of welding in the welding temperature field． Through the analysis of on-site structure monitoring data after reinforcement，the overall structural response after reinforcement was got and the safety after structural reinforcement was ensured．