The invention provides an active power control method in a wind power plant. The active power control method in the wind power plant comprises the steps of computing the active power prediction errors of all predicted points in the wind power plant, establishing a wind power plant active power prediction error distribution function, establishing a wind power plant active power prediction error distribution module, a wind power plant active power prediction confidence degree module and a wind power plant active power control module in sequence, optimizing the wind power plant active power control module, obtaining an optimization confidence weight of all unit sets, and controlling the active power of the wind power plant. The active power control method in the wind power plant is based on historical data analysis. By means of the active power control method in the wind power plant, the power-outputting error of the wind power plant is reduced, the reliability and accuracy of the wind power plant are guaranteed, and a powerful guarantee is supplied to the wind power plant in the grid-connected operation.