In order to study the dilution effect in the process of laser cladding, the temperature fields in the process of single laser cladding of 304 stainless steel under different scanning speeds are simulated. Based on the melting point of materials, the values of dilution ratio (DR) are calculated. The laser cladding experiment is conducted on the surface of 27SiMn steel. The height and width of the cladding layer and the depth of the heat affected zone are measured, and the value of DR is calculated. The element compositions of the cladding layer in different areas are analyzed. The microhardness is measured. The results show that the variation trends of DR obtained by numerical simulation and experiment are basically consistent, and DR decreases gradually with the increase of scanning speed. The higher the scanning speed, the smaller the dilution effect of elements in the cladding layer is. The nearer the spot to the substrate, the more obvious the dilution effect of element composition in the cladding layer is. The microhardness from cladding layer to substrate shows the three-stage distribution of low-high-low. The width of the high hardness zone decreases gradually with the increase of scanning speed.