Abstract: Frost is one of the main agricultural meteorological disasters restricting the production of the pear. The study on frost index of pear could provide effective reference for frost forecast, monitoring, early-warning, frost risk assessment as well as disaster prevention. Here, we conducted simulated frost experiment of the critical temperature and time of frost suffering duration in full blossom and young fruits of pear using plant growth chamber. The results showed that: lethal temperature of pear floral organ was -4℃. For pear blossom, light frost would happen when temperature lasted 2 hours at -3℃, and then became medium frost when the time reached 2.5 hours; heavy frost would happen when temperature lasted above 3 hours at -3℃, or above 0.5 hour at -3.5℃ or when temperature was below -4℃. The cold resistance of‘Manao’was better than‘Ganquan’ and‘Xingao’. For young fruits of pear, there were the little differences between three varieties. Light frost would happen when temperature lasted 2-3 hours at -2℃ or 1 hour at -2.5℃; it could become medium frost when temperature lasted 2-3 hours at -2.5℃ or 1 hour at -3℃; heavy frost would happen when temperature lasted 4 hours at - 2.5-- 2℃ or above 1 hour at - 3℃ . In addition, before temperature reached lethal temperature, young fruits of pear would suffer more seriously when its diameter was smaller or the time of low temperature was longer.