The invention provides a refining method for aluminum alloy. According to the method, Al-Ce binary amorphous alloy is used as an aluminum alloy refining agent, and the atomic percent of Ce in the Al-Ce binary amorphous alloy is 7 to 10%; and the refining agent is an amorphous material and can provide a great number of uniformly-distributed nanometer nucleation particles after added into an aluminum melt, so the refinement effect of A356.2 alloy is substantially improved. The method is simple, has a short production period and overcomes the disadvantages of complex process, long process time, limited refinement effect and the like in conventional melting and preparation process.