The invention provides a reinforcing agent for reinforcing effect of anticancer drugs to obtain an outstanding therapeutic effect for cancer. The invention relates to a settling method of the anticancer drugs effect reinforcing agent, characterized in that, the effective constituent of which is nitrous oxide. Based on the invention, the reinforcing agent can generate unexceptionable therapeutic effect for the non small-cell carcinoma of the lung which is not to build effective therapeutic method for progressivety cancer at present, and can not perform surgery, and is one of cancers most difficult to apply chemotherapeutics.