Abstract: By using indirect hemagglutination assay (IHA)，807 nonvaccinated serum samples collected from partial intensive pig farms of Henan area were tested for antibody against PCP. The results were as follow: 30.11%(243/807) checked sera antibody titers were ≥1∶8 which was regarded as positive.The positive rates in sows,postweaning piglets(40-day-old)，growing pigs(80 to 100-day-old),growing pigs(150 to 180-day-old) were 56.94%(123/216)，9.04%(17/188)，27.65%(60/217) and 23.12%(43/186), respectively. The geometrical average value of antibody titers of positive pigs were 1∶65.15, 1∶11.53, 1∶26.92, 1∶19.73 respectively.

Key words: porcine; contagious pleuropneumonia; indirect hemagglutination assay (IHA); titer