Welding deformation in arc welded lap joints of thin steel plates with different strengths were quantitatively investigated by experimental measurement and numerical simulation. Four welding deformation components were discussed in detail. There is a relatively uniform distribution of transverse shrinkage along the welding direction and a largest angular distortion in the middle transverse section. The bottom plate of the lap joint presents larger longitudinal shrinkage and deflection obviously in comparison with top plate. Two lap joints with different strength were discussed comparatively. It is observed that the DP590 lap joint with higher strength has larger angular distortion and smaller shrinkage and deflection in the longitudinal direction, and no obvious variation in transverse shrinkage. Correlation between material properties and welding deformation of arc welded lap joints were investigated by parametrical numerical simulations. The results show that the welding deformation varies considerably among various steels with different yield strength (YS) and coefficient of thermal expansion (CTE) although they have the same heat input.