Diel and seasonal changes of carbon dioxide emission from Mollic-Cryic Cambisols on degraded grassland were studied. The results indicated that: (1) Diel maximum rate of CO₂ efflux appeared at 12:00-16:00 and minimum at 4:00-8:00. Rate of CO₂ efflux in the daylight was greater than that in the night. (2) There were significant seasonal dynamic and phenophase changes in rate of Cqemission. Diel average rate of CO₂ emission was 320.86±130.49mgm^-2h^-1.Phenophase variation was exuberance>withering>green up. (3) Diel change course of rate of CO₂ emission was controlled by air temperature and soil surface temperature. However, the correlations between seasonal dynamic of rate of CO₂ emission and air temperature, soil surface temperature, and temperature of each layer of soil (5cm, 10cm, 15cm, 20cm, 30cm) were very significant (P<0.01). (4) The rate of Cqemission from Mollic-Cryic Cambisols on the over grazing pasture is lower than that on the moderately grazing pasture.