The invention belongs to the technical field of a power system and especially relates to a power transmission line wildfire dynamic forecasting and early warning method based on sequential variation. The method is characterized by, to begin with, constructing a wildfire spreading ellipse model at the initial time t0 according to wildfire point initial position F0, wind direction and wind speed and slope information, and calculating wildfire maximum spreading speed Vmax at the current time; calculating the minimum distance D0 between the F0 and a power transmission line L at the time t0 and spreading speed VL0 in the direction, and determining power transmission line wildfire early warning grade at the time t0; determining speed of the fire point F1 in the power transmission line spreading direction at the next time t1; calculating a wildfire spreading model obtained from the time t1 and after a time period delta t; repeating the steps above until obtaining a series of wildfire point positions about time series; and when receiving fire point F0 spreading and ambient environment change information at any time, updating a new wildfire spreading path diagram in time starting from the time. The method can correct wildfire spreading forecasted paths in time, and has the advantages of small calculation amount and clear target and preventing simulation in irrelevant direction.