To provide a method for searching an anti-alkylating substance that inhibits/repairs alkylation inducing O6methylguanine among alkylations, and to obtain anti an alkylating agent searched by the method.

The method for searching the anti-alkylating agent that inhibits alkylation levels comprises measuring the expression level of fused gene having an alkylation-repairing gene that recognizes O6methylguanine and adding a substance to be tested to an alkylated DNA of a host cell induced by the addition of an alkylating agent.