Cracking behavior of laser welded high strength alloy steel during solidification was investigated. Bead-on-plate welding was carried out with high power carbon dioxide laser system. Test coupons were prepared from hot rolled 2.4㎜ thick plates. Two important welding parameters such as travel speed and applied laser power were varied. Results showed that input energy for the welding had nothing to do with the solidification crack susceptibility. Under the tensile pre-stress of 10㎏/㎟ and 2.1㎾ laser output condition, the crack ratio was slightly decreased with increase of travel speed. Threshold stress for initiation of hot crack shows linear relation with travel speed over the test range of 700-1,100㎜/min which was the condition for full penetration; the more the speed goes up the higher the applied threshold stress is needed to develop weld hot crack.