Abstract: According to the principle of equal strength matching,the BHG-5 welding wire is selected for the conducting the Y bevel cracking test and the multi-layer and multi-pass manual welding test with different heat inputs to the 890 MPa seamless steel tube for crane boom service. The cold cracking sensitivity of the material,and the effects by different heat inputs on the microstructure and the mechanical properties of the weld joint are investigated. As a result it is revealed that when the pre-heating temperature is 150℃,the occurrence of the cold cracking can be completely avoided;and along with the increase of the heat input,the strength of the weld metal joint just changes slightly,whereas the impact toughness of the HAZ of the weld joint drops obviously. Using the heat input under 20 kJ/cm will surely get the weld joint have better strength and toughness.