Based on SYSWELD finite element code, a three-dimensional finite element model for laser remelting process was created, the wide-band heat source model implemented by a FORTRAN subroutine was developed to simulate the single-pass laser wide band remelting process on 42CrMo steel, and predict residual stresses of the remelting zones with different technological parameters were estimated and analyzed. The thermal cycle was measured by temperature measuring equipment and phase transformation was observed by scanning electron microscopy (SEM). The results showed that technological parameters has a great influence on the residual stress distribution of the remelting zone, the superficial processability of the laser remelting zone is bad whether the laser energy input density is too high or too low. The favorable residual compressive stress in the remelting zone can be achieved when the laser output power is 3500 W, the scanning rate is ranged from 600 mm/min to 1000 mm/min, that is, the energy input density is within 20.9～35.0 J/mm2. After the processing, the initial ferrite-pearlite microstructure of the matrix is transformed to martensite phase with the proportion higher than 95%.