Abstract: This paper reviews the research status of surface pretreatment and the effects of surface state on joint strength in dissimilar materials joining. Some conclusions are as follows: 1) Depositing an active metal can form well solid solubility with the base material or the filler metal in dissimilar materials joining,which can enhance the interface reaction and improve the joint strength; 2) The activity of surface elements is promoted and the diffusion ability is enlarged,the hard brittle phase in the joint is reduced and the joint strength is improved by perfecting the physical,chemical or mechanical properties of the base material.