Abstract: QT700-2 ductile cast iron was treated by single-pass and asymmetric multi-pass laser quenching processes, and then the surface hardness and hardened layer depth of the ductile cast iron under different laser quenching processes were studied. The results show that after single-pass laser quenching, the surface hardness of the ductile cast iron was 52-59 HRC; the surface hardness increased with increasing laser power, and increased first and then decreased slightly with increasing scanning speed; with laser power of 1 300 W and scanning speed of 8 mm·s^-1, the surface hardness of the ductile cast iron evenly distributed at 55-58 HRC, and the hardened layer depth was about 1 mm. After asymmetric multi-pass laser quenching with different process parameters, the surface hardness of the ductile cast iron was greater than 52 HRC; with the previous pass laser power of 1 200 W and scanning speed of 6 mm·s^-1, and the latter pass laser power of 1 300 W and scanning speed of 8 mm·s^-1, the surface hardness of the ductile cast iron was relatively high, and the fluctuation of hardness was relatively small; the width of the softened zone at 0.3 mm from the surface was about 4.0 mm, and the hardened layer depths in the non-softened zone and in the softened zone were about 1.0, 0.5 mm, respectively.