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4-N,N-dimethylamino-4'-N'-methyl-stilbazolium tosylate (DAST) is an important optical material, but its poor conductivity limits applications in devices. To tackle this problem, we designed, prepared, and systematically investigated novel binary composite films that are composed of two-dimensional (2D) DAST and 2D graphene. Results indicate that both electrical and optical properties of DAST can be significantly improved by graphene addition. The negative steric effects of big DAST molecules that greatly trouble ex-situ synthesis can be efficiently overcome by in-situ synthesis, thus leading to better film quality and higher physical properties. Consequently, the in-situ composite film exhibits a low sheet resistance of 7.5 × 10(6) ohm and high temperature coefficient of resistance of -2.79% K(-1), close to the levels of the most important bolometric materials for uncooled infrared detectors. Particularly, a new low temperature reduction of graphene oxide induced by DAST, which is further enhanced by in-situ process, was discovered. This work presents valuable information about the DAST-graphene composite films, their chemical structures, mechanisms, physical properties, and comparison on in-situ and ex-situ syntheses of graphene-based composites, all of which will be helpful for not only theoretically studying the DAST and graphene materials and expanding their applications, but also for seeking new optoelectronic sensitive materials.