Manual TIG was used to weld the dissimilar steel 254SMO/Q235B by taking ERNiCrMo-2,ERNiCrMo-3, ERNiCrMo-10 ERNiCrMo-12,ERNiCrMo-13 and ERNiCrMo-14 nickel-based alloy wire as filler metal. After welding,the welded joint microstructures were analyzed by metallurgical microscope, X-ray diffraction,scanning electron microscope and energy disperse spectroscopy. The results show that when the ERNiCrMo-2,ERNiCrMo-3 and ERNiCrMo-14 welding wire are used,a certain number of cracks will appear in weld. The studies indicate that the welding cracks are solidification cracking. The key factor to cause weld cracking is the difference of physical properties of dissimilar steel and impurity segregation. The welds with good appearance and without welding cracks can be obtained by using the other filler metals.