According to one exemplary embodiment, a smoothing method for time data sequences is performed, which includes: smoothing original data points of a time data sequence, then from smoothed data points, determining reference points for a global trajectory and a local trajectory; according to the reference points, calculating a direction of the global trajectory and a direction of the local trajectory; and adaptively calculating new data point(s) by integrating the two directions. The trajectory of new data points maintains the properties of smoothness and real-time perception.