The pathological conditions of the last transitional phase (LD50≥6.67kg/kg bw) to the the crisped grass carp and the common grass carp were compared. The length-weight relationships are significantly different between the two fish groups. The average dissolved oxygen concentration threshold increased from 0.54 to 1.68mg/Ｌ, and the threshold concentration of CO2 for (decompensation) decreased from 194 to 52.42～65.36 mg/Ｌ when common carp changed to the last transitional phase. Both Broh and Root effects also changed significantly. Histological examination shows that the change from the common Grass Carp to criped Grass Carp is a gradual process with changes in ultrastructural organization and cytochemical development of all the systems. The major reason that leads excess crisped Grass Carp to death is the blockage of blood circulation system. The toxicological effect of feeding Vicia faba L. to the fish was investigated. Results of the present study are valuable for improving the intensive production and long-distance transportation survivorship of the crisped Grass Carp.