In this study, a prediction model of paddy thermal condition was developed, which solved heat balance in two layers of crop and water to describe heat balance change with different water management. To calibrate and evaluate the applicability of proposed model, field experiment was conducted. Calculated water and vegetation temperature showed good agreement with observed data. Then by using the proposed model, the changes of paddy thermal condition with different water managements were simulated. Continuous irrigation was effective to cool down the water and soil temperature, and water depth control was also effective when relatively cool irrigation water was not available.