Winter wheat is.one of the main grain crops in China. North China Plain (NCP) is one of the most important areas for winter wheat. It is necessary to select suitable sowing date for winter wheat to study the influence of climate warming on heat conditions before green-up stages in NCP. In this paper, daily time-series meteorological variables during the period of 1961 2010 at 52 stations and phenology of winter wheat during the period of 1992 2009 at 39 agro-meteorological stations were jointly used to study the relationship between key phenology and critical temperature. Meanwhile, characteristics of spatial and temporal distributions of heat conditions before green-up stages, including the end date of air temperature≥0℃ stably (EDO)，the first date of air temperature ≥2℃stably (FD2),the days of winter dormancy, and negative accumulated temperature (Tnacc) during winter dormancy,were analyzed in NCP. The results show that there were close relationships between sowing date of winter wheat in different regions and different critical temperature, which were the end date of air temperature≥16℃ stably (ED16) in the northern NCP， the end date of air tem- perature≥15℃ stably (ED15) in the middle NCP,and the end date of air temperature≥14℃ stably (ED14) in the southern NCP. Meanwhile, the statistics are significant between winter dormancy date and the end date of air temperature≥0℃ stably， between green-up date and the first date of air temperature ≥2℃ stably. Temporally， it becomes later for winter dormancy date during the past 50 years; on the contrary, it is earlier for green-up date with climate warming. For the days and negative accumulated temperature during winter dormancy, they decrease slowly for the past 5 decades. Spatially, regions with higher latitude have earlier sowing dates and winter dormancy dates. In reverse, there are later green-up dates in those higher latitude regions in NCP. In terms of the days and negative accumulated temperature during winter dormancy, they reduce when the latitude decreases.