A carbon nano paper monitoring method of a polymer-based composite material curing process is provided; a rectangle structure is cut from carbon nano paper, and a four-probe resistance measuring instrument is fixed on the surface of the carbon nano paper, to form a sensor; the sensor is embedded to the interior of a composite material, curing molding is carried out according to a composite material curing technology system, the change of the carbon nano paper resistance in the composite material curing process is measured by the four-probe resistance measuring instrument, a carbon nano paper resistance-temperature-time relationship curve of the composite material curing process is made, and related information about the gel point/time and the resin curing process and the like can be obtained from curve mutation points, so as to be used for guiding regulation and control of composite material curing technology parameters. A three-dimensional network structure of the carbon nano paper has good interface bonding property with the composite material, can be subjected to integrated molding with the composite material and does not affect mechanical properties of a composite material structure; and besides, the problems that the scale of an optical fiber sensor is large and embedding can affect structural performance are overcome.