Abstract: Accumulated temperature above 10℃ is one of the important indices of thermal condition.The research on characteristics of accumulated temperature variation in time and space scope and their effects on agricultural production has become more important with the appearance of abnormal climate and the requirement in agricultural production.Through analysing some characteristics of accumulated temperature(above 10℃) variation in China,it is found that in the recent century there are three phases in variation of accumulated temperature in China:cold,warm and cold.They are reversed in 1930’s and 1950’s respectively.Through calculating and analysing the standard deviation of accumulated temperature above 10℃ in various regions it is noticed that there are some small fluctuations in the cold trend of climate during the last 30 years and they have certain effects on agricultural production in various regions.In order to compare the stabilities of accumulated temperature above 10℃ in various regions,the coefficients of variation of accumulated temperature above 10℃ are calculated.The C_V values increase with increasing of latitudes in space and they are correlated to accumulated temperature (less 6000℃) with exponential. Various guarantee(accumulated probability) curves of accumulated temperature above 10℃ for different length of data-series are compared.It is shown that these curves are more stable when the length of data-series is over 50 years.In addition,guarantee curves in different regions are compared,too.Their characteristics and classification are studied preliminarily. According to the slope of guarantee curves within 10-90%,various guarantee curves in different regions in China are classified into three types:stable, instable and neutral. In the end,the relationship between guarantee and return period is also analysed and disccused.It is suggested that guarantee is related to return period with opposite if their non-biased estimators are omitted,