Abstract: This study presents modeling of dissolved oxygen performance in a greenhouse fishpond. A short-term Disolved Oxygen (DO) fluctuation of a fishpond was developed by using various simple equations and continuous measurement of DO, temperature and solar intensity. Numerical computation has been performed for a typical winter day at the month of January, 2007. Components considered in the DO model include the production of DO by phytoplankton and consumption of oxygen by phytoplankton, fish, water column and sediment. Numerical equations were solved with Excel soft ware to predict DO in the pond. Initial slope (α) and P_max were calculated from DO production Vs. solar radiation curve. The amount and distribution of oxygen production in the water column depend on solar intensity and penetration as well as phytoplankton concentration. A parametric study has been performed to represent the effects of pond depth, SDD, extinction coefficient, water temperature and fish yield changes on DO regimes in fish pond. Dissolved oxygen concentrations in the pond varied with both pond depth and SDD. By increasing the depth of the pond and of the SDD and maintaining phytoplankton chlorophyll-a concentration at 232 μg L^-1, the overall oxygen production was increased. The low DO values in the shallow pond (0.5 m) with a high SDD (0.5 m) when compared to other ponds with SDD equal to their pond depths, was the result of low overall oxygen production relative to the demand by sediment and fish which were same for all depths of pond. Predicted and experimental DO concentrations exhibited fair agreement with correlation coefficient of R = 0.99 and root mean square percent deviation e = 3.73%. Such correlation between predicted and experimental data indicates that the assumption inherent in the computer model of the processes is valid for the DO production and consumption in the pond.