Abstract: The experiments were conducted to study the effects of soil conditioner on root activity and photosynthetic parameters of cabbage. The results indicate that soil conditioner could damage the relatively compacted condition of soil, and make porosity contributed reasonably. Treatment with 2(dw2) and dw1 could separately make the bulk densities decline by 7.3%, 1.9% and 4.6%, 1.3%, separately and make the porosity increase by 9.3%, 2.8% and 5.9%, 1.9% in soil layers of 0～20 cm and 0～30 cm, respectively. Compared with control, the CEC(cation exchange capacity) of dw2 increase by 5.7% and 10.9% in soil layers of 0～27 cm and 27～45 cm, the root activity of cabbage was significantly different, and the diurnal changes of Pn were influenced, with increasing the capability of photosynthesis and improving the adaptability to light intensity.