The invention discloses a manufacturing method for ohmic contact with low specific contact resistance and low roughness. The manufacturing method is characterized in that hardly compatible Mo metal is introduced to an ohmic contact metal seed to form a TiAlNiMoAu combination, thus the surface roughness and the specific contact resistance after alloying are reduced under the same alloying condition. In the manufacturing method, the low diffusivity of the Mo is utilized, and a binary alloy phase is matched, thus low contact resistance is realized, the roughness of the ohmic contact after alloying is also reduced, the overlay accuracy of a photolithographic process is improved, the number of process steps is reduced, the stability of the ohmic contact is improved, and a firm foundation is established for device process practicability.