Three specific primer pairs were designed based on the conserved sequences of different genotypes of the grass carp reovirus (GCRV). 530 bp, 297 bp, and 196 bp DNA fragments were amplified and through optimizing the reaction conditions and system, a was established to detect the three genotypes simultaneously. Further studies indicate that the multiplex-PCR has good amplification efficiency, specificity, and sensitivity. The detection limit was 260 copies/μL, 190 copies/μL, and 230 copies/μL for The specificity experiment indicated that the primers were strictly genotype-specific. This method provides a significant improvement in the detection, genotyping, and molecular epidemiological The detection results of 86 samples collected from 16 cities in the main grass carp breeding area in China using the established multiplex-PCR method revealed that the positive rates of genotypes I, II, and 9.3%, 45.3%, and 2.3%, respectively. The positive co-infection rate of types I and II was 5.8%, that of types II and was not detected. The multiplex PCR for the three genetypes of GCRV were highly specific for the corresponding virus genotypes, with high sensitivity. Preliminary epidemiological data analysis by multiplex PCR indicates that type II is the most common genotype, and the phenomenon of combined infection of different genotypes are in general population of grass carp.