Abstract: Used GFS-3000 portable photosynthesis-fluorescence measurement system studied the net photosynthesis rate (Pn), transpiration rate (E), stomatal conductance (Gs) and intercellular CO2 concentration ( Ci) in the growth and development on six species cassava. The results showed that net photosynthesis rate （Pn）was increased in the earlier stage of growth period,and decreased in the late growth stage. The change of transpiration rate (E) and intercellular CO2 concentration was not affected by stomatal conductance (Gs) completely. The net photosynthesis rate (Pn) of South China 6（SC6） and South China 7（SC7） was higher than other cassava varieties significantly,and the Pn of South China 205（SC205） and South China 5（SC5） was higher than South China 9（SC9）.However, there was no obvious difference bewteen SC205 ,SC5 and South China 8（SC8）