Abstract: During the gas mixture flowing from bottom-hole to wellhead, the temperature of gas stream always lowers. If water exists, the hydrate formers in gas stream form hydrates certainly when the temperature of gas stream is lower than the hydrate formation temperature. Hydrates in well-hole will block the tube and stop the gas production. According to the temperature profiles in a flowing gas well and the hydrate formation temperature in well-hole conditions, hydrates in tube can be predicted. In this paper, the cause and basic regularity of hydrate formation in gas well are discussed. A method for predicting hydrate formation in a flowing gas well is presented. Comparisons between the model’s prediction and field data indicate that the model’s prediction is highly accurate.