Abstract: The 2.0% chitosan-oligosacchrides was applied on controlling of the pepper fusarium wilt, mosaic viruc and phytophthora blight. In the early days of the pepper fusarium wilt or mosaic viruc, the effect of prevention and control of the pepper fusarium wilt reached to 69.03%~73.91%. The effect of prevention and control of the pepper mosaic viruc was 81.38%. When the phytophthora blight was taken bad, the pepper was spryed the 2.0% chitosan-oligosacchrides .The infected plant percentage of the pepper phytophthora blight was controlled effectively. It was the suitable concentration of controlling of the Pepper fusarium wilt that 2.0% chitosan-oligosacchrides was diluted 500~800times.The 500 times diluted solution was the appropriate concentration to control the mosaic viruc and phytophthora blight.