The formation of nature gas hydrate can affect the normal oil DdDd gas production seriously in the development of oilfields, and this problem happened during the production of deep wells in Tarim oilfield. This paper establishes the hydrate formation model using the method of statistical thermodynamics by analyzing the hydrate formation mechanism. On the basis of analyzing the suitability of various control techniques and the actual situation that most of the well in tarim oilfield are deep well, the downhole throttling technique is selected to prevent the formation of gas hydrate. The position of gas hydrate formed in wellbore can be predicted correctly according to the change of the temperature and pressure. The design models and its methods is given for the downhole throttling technique, so the depth and the best diameter of throttling choke can be designed. The downhole throttling technique has been applied in Tarim oilfield, and the result is significant.