Cast steels AAR M 201 with different preheating temperatures and groove forms are welded with low alloy and high strength steel ASTM A588. The tensile, bending and impact tests are performed on welded joints to determine the welding process of cast steel structure. The results show that for butt joint of 8 mm and below,the preheating and interpass temperature must not be lower than 150 ℃ ;for butt joint of 8 ～20 mm,the preheating temperature must not be less than 300 ℃.Both 8 HV and 10 DHV,the welded joints have good tensile strength, plasticity and toughness,and welded joints with 180°bending are qualified. Both weld and heat affected zone,welded joints have good low temperature impact toughness.