A method for manufacturing an NO.sub.2 gas sensor for detection at room temperature comprises: manufacturing a metal electrode on a surface of a flexible substrate; manufacturing an SWCNTs/SnO.sub.2 sensitive film; and bonding the SWCNTs/SnO.sub.2 sensitive film with a portion of the surface of the flexible substrate with the metal electrode, so as to form the NO.sub.2 gas sensor for detection at room temperature. The present disclosure solves the problems of the poor adhesion between the sensitive material and the flexible substrate, and a non-uniform distribution, and achieves the purposes of secure bonding between the sensitive material and the flexible substrate, and uniform distribution.