In this paper,in comparison with their WSSVresistant characteristics,35 selective breeding families of the 4th generation and no selected shrimp of Litopenaeus vannamei were divided into three groups:relatively high resistant families,mid resistant families and susceptible families,with the average survival rates of 24.45%±6.56%,10.70%±1.41% and 2.72%±2.76%,respectively after 10³ copies WSSV/g(body weight)infection,which were significantly different among the three groups(P<0.01).Injected WSSV of 10²,10³,10⁴ and 10⁵ copies WSSV/g,the survival rate of the relative high resistant family 12 was 100%,23.3%±3.5%,7.8%±1.9% and 0 %,respectively; and the survival rate of the mid resistant family 7 was 87.7%±3.8%,12.2%±1.9%,0% and 0%,respectively; and the survival rate of the susceptible family 4 was 54.4%±3.8%,2.2%±1.9%,0% and 0%,respectively; and the survival rate of non-selected was 51.1%±5.1%,0%,0% and 0%,respectively.In comparison with mid-resistant family 7,susceptible family 3 and non-selected shrimp,the THC in relatively high resistant family 12 increased by 20.7%(P>0.05),36.7%(P<0.05)and 34.4%(P<0.05)compared with that of the abovementioned shrimps,respectively after 10³ copies WSSV/g(body weight)infection; the PO activities increased by 40.0%(P<0.05),76.3%(P<0.05)and 63.4%(P<0.05)compared with that of the abovementioned shrimps,respectively; the SOD activities compared with 31.1%(P>0.05),58.8%(P<0.05)and 32.0%(P>0.05)increased by that of the abovementioned shrimps,respectively; the POD activities compared with 29.64%(P>0.05),44.9%(P<0.05)and 43.3%(P<0.05)increased by that of the abovementioned shrimp s,respectively; the content of plasma protein compared with 31.2%(P>0.05),38.7%(P<0.05)and 39.3%(P<0.05)increased by that of the abovementioned shrimps,respectively.However,there were no significant differences of the THC,PO,SOD,POD and content of hemolymph protein among midresistant family,susceptible family and non-selected shrimp.After 4 generations of selection,the immune capability of the shrimp from relatively high resistant family was much higher than that of the other groups and nonselected shrimp,with apparent powerful capability of WSSV resistance.These findings would help to direct the future selective breeding of shrimp for WSSV resistance.