Abstract: Cold damage was one of the main meteorological disasters on florescence of Dangshan crisp pear,so risk assessment for cold damage was very important.Risk assessment model for cold damage to florescence of Dangshan crisp pear was established by using mathematical statistics methods based on the phenological data and meteorological data from 1983 to 2006,especially considering the probability distribution of the daily minimum temperature during florescence.The results showed that the cold damage risk levels during florescence of Dangshan crisp pear could be expressed with the probability of cold damage during flowering beginning multiply the total probability of cold damage during florescence day to day.As usual,the cold risk was more serious if flowering beginning was earlier or florescence was longer.The date of flower beginning accorded with normal distribution,that is,the probability of cold damage from flowering beginning too early or too late would be small.The cold damage during florescence of Dangshan crisp Pear suffered could be divided into three levels,depending on daily minimum temperature ≤7℃,≤ 5 ℃,≤ 3 ℃ respectively.There was an exponential relationship between the total probability of cold damage after flowering beginning and the date of the flowering beginning,but there was a linear relationship between them if cold damage below or equal to 3℃ occurred at the date of flower beginning.

Key words: Old Course on the Yellow River, Old Course on the Yellow River, Forescence of Dangshan crisp pear, Cold damage, Risk assessment