The e0ffect of climate and plant on pollen concentration in the air is discussed. Based on the analysis of the observed data of Hexi district meteorological mast station and Nanjing Road of Heping district meteorological station between April,1994 and Oct.2000,it is found that the change of cyclical and seasonal nature of pollen concentration is clear in a year.The correlation of the observed pollen number in that day,daily range of temperature,and departure of mean daily temperature with number of pollen concentration in the next 24 hours is significant. Using these factors, predictive equations of pollen concentration day by day for Spring, Summer and Autumn were established, respectively. The multiple correlation coefficients of the equations are 0.73 and 0.76, respectively, and they have passed F-test.At the same time,the equations are modified by the essentialy factors of precipitation, wind, cloudage as well as phenophase of plant and the forecast accuracy is satisfactory.