Abstract：Recent years，root rot of watermelon has caused more and more serious damage to watermelon production in some area of China.We studied the biological characteristics of the pathogen in order to provide the basis for the watermelon breeders to screen the resistant germplasm resources and select resistant watermelon cultivars to the disease.The results are showed as follow：The temperature affects pathogen growth greatly，the range of temperature for the pathogen growth is 10～40℃，and the optimum is 30℃；The pathogen can grow at the range of pH4～10，and the optimum is pH8；It can utilize many kinds of carbon sources very well；Nitrogen nutrient has a strong effect on the growth of the pathogen，and nitrate-nitrogen[NO3-N]is suitable for its growth，but ammonium-nitrogen[NH4-N]does not favor the pathogen；Both the temperature and relative humidity are the key factors for the conidia germinating，and 100% and 25～30℃ are the optimal relative humidity and the optimal temperature for the conidia germinating，separately；The conidium lethal temperature is 58℃，5 minutes lasted.
