A new way of dividing the year into four seasons is discussed and then applied to various regions in China based on the five day means for air tem-perature of 84 stations and phenological reports of several stations. The four seasons are defined as follows:Spring or Autumn = mean 5-day temperature 10°-22℃.Summer = mean 5-day temperature above 22℃.Winter =mean 5-day temperature below 10℃.