Abstract: The susceptibility to grass carp reovirus (GCRV) of CAB-80, BCC, PHG, GCE GCTF-2 and GCK-84 (these cell lines were derived from crucian carp blastula embryos, herbivorous bream caudal fins, loach haploid gastrula embryos, grass carp gastrula embryos, grass carp caudal fins and grass carp kidney, respectively), as well as four clones isolated from GCK-84, were analyzed comparatively. Sensitivity of various degrees was confirmed in the infected cell lines (except PHG) among which GCK-84 was the most sensitive. It is demonstrated that GCRV, in vitro, has no strict species specificity. Typical symptom of muscular hemorrhage could be replicated when fingerlings of grass carp were infected with the virus which had been propagated in GCK-84. The virus produced by GCK-84, GCRF-2, CAB-80, BCC and PHG was titred in GCK-84 cells. The titers (TCID50/ml) were 8.24, 7.36, 2.90, 2.15 and 1.33 respectively. Sicells. difference was also observed in the four clones and GCK-84, with the titers ranging fro6.3 to 9.32. The results prescnted above predict the relative potential significance in the disease-resistant breeding of fish cell engineering.Serious damages in GCRV-infected GCK-84 cells could be seen with electron microscopy. The observed virus was in the shape of spherical particles having a size of 58 nm in diameter and a core with high electronic density approximately 38 nm in diameter on the average. The distribution of virions in cells could be divided into three patterns: existing individually in cytoplasm, congregating in large crystalline aggregates bound by membranceous structures, gathering together in an orderly or disorderly arrangement without a surrounding membrane.