Abstract: Growing period is an important indicator of growth and development of crops and utilization of agricultural climate resources．The start and end times and total period length are important in guiding agricultural production and in coping with climate change．The three major grain crops of rice, maize and wheat are examined．Variations in growing period definition for different crops and in different regions in China are described．Applications of growing period definition to growing period variation and characteristics of climate change during growing period are reviewed．The start and end dates of growing period are defined mainly according to critical temperature or practical experience．Critical temperature is an important climatic indicator in crop growth and development．Temperatures of 0, 5 or 10 °C are used as main thresholds to accurately estimate specific dates of planting and harvesting by the moving average method in China．It is suitable for the definition of starting and ending dates of growing period on local scale．Agricultural practices and the actual situation of grain production in China are also used to directly select the growing period．It is convenient to carry out long-term evolution of climatic factors on regional scale. Improved definition of growing period could better determine growing period of crops, and are helpful for the accurate analysis of regional climate changes, helpful also for the selection of indicators and parameter optimization in climate change research．This also facilitates the formulation of agricultural planting systems and optimization of crop variety layout, ensures crop yields, improves production potential of crops．