Based on the high verticalresolution position data of Lband and radiosondes, three schemes for calculating secondlevel wind speed are designed by selecting different time windows at different sounding heights. The calculated secondlevel wind speed and ERAInterim reanalysis data are compared on different indexes: the amount of data, the average deviation (Bias), and the root mean square error (RMSE), which indicate the optimal algorithm to calculate the second wind speed. The results show that the appropriate length of time window is necessary to accurately calculate the second wind speed. Given the radar positioning system deviation, the second wind speed error will be larger if the time window is chosen too large or too small. Based on the ERAInterim reanalysis data with good spatial and temporal consistency, this paper presents a new scheme to evaluate the Lband secondlevel wind speed calculation.