Abstract: Diurnal changes and seasonal changes of net photosynthetic rate( Pn )and chlorophyll concentration of Magnolia denudata leaf in different growing stages and different positions of crown were studied.The results revealed that there is a single apex for Pn at initial growing stage,except upper part of crown in sunshine side is double apex.many apex at fast growing stage,crown in sunshine side is many apex and crown in shade side is double apex at last growing stage.The Pn at fast growing stage at greater than that at last growing stage,and that at last growing stage was greater than that was initial growing stage.The effects of direction and position of crown on Pn at initial growing stage was not notable,the effects of which at fast growing stage were very notable,the effects of position at last growing stage was notable.The factors effecting net photosynthesis rate and the content of chlorophyll also were analysed.