This standard specifies the test instruments and tools, samples, environmental conditions, test procedures, test results and test reports for prepreg gel time. It is suitable for the determination of prepreg gel time. The principle of the method is to put the preheated prepreg sample between the Microscope coverslips to apply pressure and record the time when the Resin is no longer filamentous. The test instruments and tools include electric heating plates, stopwatches, Microscope coverslips, probes and surface temperature meters. The sampling method and quantity of the samples are specified according to the material technical conditions. Before sampling, the preprepreg temperature should be raised to Environmental temperature.