The invention discloses nickel base alloy powder for overlaying welding of the sealing surface of the intake and outlet valve of automobiles. The nickel base alloy powder comprises the components with the following weight portions of 25-27 percent of Cr, 4-6 percent of Mo, 10-15 percent of Fe, 2-3 percent of Si, 1.5-2 percent of B, 0.65-0.75 percent of C and Ni for the rest. The beneficial effects of the invention are (1) low cost, (2) good technological properties and (3) high hardness. The nickel base alloy powder can take the place of cobalt base alloy powder and has low cost. The price of the nickel base alloy powder is one third of the price of the cobalt base alloy powder. The nickel base alloy powder is especially suitable for plasma overlaying welding technology and vacuum furnace melting technology of the sealing surface of the intake and outlet valve of automobiles and locomotives. Compared with Stellite No. 6 cobalt base alloy powder, the welding layer of the invention processed by the same plasma arc overlaying welding technology has a same volume loss (mm <3>) in wear test. By comparing the hardness of the nickel base alloy powder with the hardness of the Stellite No. 6 cobalt base alloy powder, the two powders have the same hardness HRC which is 43 after the powders are cooled to room temperature. The two powder after being welded have the same hardness under 400-700 centigrade temperature in the furnace, while the nickel base alloy powder has better red-hardness.