Ice nucleation test of bacterial suspension of Erwinia sp strain 256 indicated the ratio between of the number of ice nuclei and number of bacterial cells in a culture was found to vary with incubation temperature、growth medium and composition、culture age.optimal condition for ice-nucleus production of ice nucleus bacterium included:incubation of the bacterial cells at 20~24℃ on nutrient agar containing 5% glycerol by 6 days. physical and chemical agents have different effect on ice nucleation activity