Turbulence gives effect on the light propagating in the atmosphere. There is an important parameter describing the turbulent strength which is the optical-wave refractive-index structure constant. Analyzing the echo of wind profile radar provides a new method to study turbulent strength. Calculating the turbulent dissipation rate and vertical gradient of mean velocity using wind profile radar, and combining the data of meteorological parameters, the optical-wave refractive-index structure constant C2n can be estimated. The order of magnitude of C2n is 10-18~10-13 m-2/3. The results are coincident to the actual condition, which proves that the new method is feasible. The effect of pressure gradient, temperature gradient and humidity on the refractive-index structure constant on different isobaric surfaces is simulated simultaneously. The results show that: pressure gradient can be ignored because of its small effect on C2n, while temperature gradient may have large effect on C2n, so there should be higher precision in actual measurement. The variation between 10% and 90% of relative humidity causes less than one order of magnitude of C2n, which demonstrates humidity can be ignored in clear air.