The invention belongs to the communication technical field and particularly relates to a round trip time forecasting method based on adaptive filtering. The method comprises the following steps: setting the initial values of a base number m and a variable i; measuring m-numbered successive RTT values when the variable ranges from i to m+i-1; forecasting the (m+i)th RTT value according to the filter weighting coefficient vector and forecasting base parameter vector; modifying filter weighting coefficient vector according to the forecasted (m+i)th RTT value and the measured (m+i)th RTT value; adding 1 to the variable I, and forecasting the next RTT value. The method of the invention utilizes the self-similarity of RTT, uses the m-numbered measured RTT values on data transmitting end and adopts the adaptive filtering method to forecast the next RTT value, thus achieving the aim of accurately forecasting RTT value.