The invention discloses nickel-molybdenum-chromium-diamond alloy composite powder and a preparation method and application thereof, and belongs to the field of diamond composite material processing. The nickel-molybdenum-chromium-diamond alloy composite powder comprises the following components of, in percentage by weight, 35-60% of diamond, 9.2-17.6% of Mo, 3.6-9.4% of Cr, 0.2%-0.65% of Fe, 0.2%-0.65% of Co, and the balance Ni. According to the diamond alloy powder, the excellent corrosion-resistant, wear-resistant and anti-oxidation functional composite powder materials is provided for 3D printing, thermal spraying, powder metallurgy, hot-pressing sintering and the like.