The invention discloses an EPON traffic forecasting method. The method comprises the following steps: forecasting the next frame arrival time and the duration of a next transmission cycle by using a least mean square polynomial, and dynamically allocating bandwidth for the next transmission cycle; and enabling an ONU to estimate the amount of data cached in the current phase according to two amount of time, and proposing bandwidth allocation requirements to an OLT. The algorithm is applied to the ONU, can be compatible with a multi-point control protocol, and can achieve the optimization of frame transmission delay under lower algorithm complexity and implementation cost.