Provided is a method for preparing nickel-aluminum alloy powder at low temperature, which is simple and economical and is capable of solving the reactor corrosion problem. The method for preparing nickel-aluminum alloy powder at low temperature includes: preparing a powder mixture by mixing nickel powder and aluminum powder in a reactor and adding aluminum chloride into the reactor (S1); vacuumizing the inside of the reactor and sealing the reactor (S2); and preparing nickel-aluminum alloy powder by heat-treating the powder mixture in the sealed reactor at low temperature (S3).