By researching responses of leaf net photosynthetic rate on wild buckwheat and tartary buckwheat to light,temperature and change of soil water content,it shows that responses of leaf net photosynthetic rate are different.Wild buckwheat is superior to tartary buckwheat in using the energy of photon,the suitable temperature range of leaf net photosynthetic rate,the adaptability for water deficit,they have higher photosynthetic efficiency and better duration.