Many simple and integrated annual or seasonal climate factors have commonly been utilized in the research of atmosphere science, geosciences and ecology to express characteristics of climate and its variations, as well as to predict climate and environment relationships and their future changes. In the international global change research, especially in vegetation modelling,however, scientists usually used bioclimatic factors to simulate and analyze quantitative relationships of vegetation structure and functions to environments. These variables include, for example, mean annual temperature, mean temperatures of the coldest and warmest months, extreme low temperature, mean annual precipitation and its seasonality, growing degree days at 0℃ and 5℃ base, some drought or moisture indexes such as the plant-available moisture index alpha (a ratio of actual to potential evapotranspiration),Palmer Drought Severity Index (PDSI),and Standardized Precipitation Evapotranspiration Index (SPEI). Some of these variables have not been paid more attentions,especially in domestic palaeoecological and palaeobotanical studies. These variables have not been frequently utilized by palynologists when numerically reconstructing past climates using pollen records. This paper introduces firstly some bioclimatic factors and their controls on the distribution of species and vegetation. Then,some bioclimatic factors that commonly used in global vegetation models and past climate reconstructions are emphasized, including their principles, calculation methods, advantages and disadvantages,and applications. Some easily accessible climate data and databases are finally enumerated for further downloading and using,for example, the climate databases from the Climate Research Unit (CRU) and WorldClim, climate observations and interpolated data from China's Climate Data Center,and the climate database under the Chinese terrestrial ecological information system of the Chinese Ecological Research Network.