Abstract: The effect of phytohemagglutinin on the immune efficacy of Newcastle disease vaccine was studied with Avian chickens as experimental animals. After the maternal antibody level was detected, 90 chickens with antibody level of 2.5 log2 were selected and randomly divided into three groups, that is, the control group, the single immune group, and the PHA group. The chickens of the single immune group and the PHA group were immunized with LaSota attenuated vaccine, when they were 7-day-old and 21-day-old. And each chicken of the PHA group were administrated 0.01 ml PHA via intramuscular injection. The titers of antibodies against NDV were respectively determined at 14, 21, 28, 35, 42, 49, and 56 d post the first inoculation. The results showed that the HI antibody titers against NDV were higher in PHA group than in another two groups with significant difference （P〈0.05）, indicating PHA may greatly strengthen the immune efficacy of LaSota attenuated vaccine on chickens.