Abstract: To get the CDO (Critical Dissolved Oxygen) of gasping for air and Pan Tong for Grass carp in spring, we carried out several simulation experiments in Jingzhou Agricultural Meteorological Station in spring. The results indicated that, the CDO of gasping for air and Pan Tong for Grass carp in spring was 0.30, 0.10 mg/L and lasted more than 30 min respectively. The results also showed that, there was a direct relationship between water turbidity level and dissolved oxygen ability of water body. The DO increment of pond water oxygenated in 14 hours was 1.98 mg/L higher than mild turbid running water oxygenated, and the DO of replacement of running water had been raised by 1.2-1.6 mg/L. So special attention on water quality should be paid in pond culture of fish in spring, and there would be a greater improvement of fishes’ living environment if water quality was improved, and gasping for air and Pan Tong might be held off or reduced to some extent, thus greater economic losses would be avoided.