The present work aims at developing an analytical model for evaluating the thermal radiation of a fire plume formed by burning wildland fuels at a given burning intensity and crosswind. By resolving the equations governing gas continuity, momentum, and energy conservation for a convective (buoyancy) plume, gas velocity and temperature profile along the central line of the plume were determined, which enables a quantification of radiation intensity of flame and buoyancy plume zones. Model features are examined, and the predicted results are compared with the available experimental data. It is found that for a fire with burning intensity exceeding 600kWm-1, the radiant heat emittable from its plume is not only contributed by the luminous flame zone but also by the buoyancy plume significantly. This indicates, for the first time, a necessity of inclusion of the contribution of the buoyancy plume in evaluating thermal impact of a fire plume on a receiver in the environment. The current work provides an important basis for convenient but reliable assessment of the fire risk of buildings raised by the occurrence of a wildland fire in adjacent areas.