A method of estimating atmospheric optical turbulence is introduced which is called support vector machine (SVM). Based on this method, the gradient of temperature, wind speed, and relative humidity are used to calculate the refractive structure parameter C2n in Chengdu, Sichuan from 2014-5-13 to 2014-5-18, which is a continuous 6-day estimated result. The estimated results agree well with the measurement results, which can basically show the characteristics of optical turbulence in Chengdu area. Compared with results of Wyngaard algorithm, the results of SVM are more consistent with the measurements, and the estimation accuracy at night is higher than that of the Wyngaard algorithm. The relative analysis demonstrates that the correlation coefficient between the estimations and observations is over 80%. Besides, mean absolute error and mean relative error prove that after training, SVM can precisely estimate C2n in Chengdu. However, deviations are found between estimations and measurements during the transition time, which should be overcome to improve the performance of the model.