The aim of the present paper is to study the behaviour of crown forest fires propagating through crown canopy and to study the mutual influence of crown forest fires and boundary layer of atmosphere using numerical simulation with a physics-based model. It is a coupled atmosphere/crown fire behavior model and is based on conservation of mass, momentum, species and energy. The boundary-value problem is solved numerically using the method of splitting according to physical processes. It allows investigating dynamics of forest fire initiation and spreading under influence of various external conditions: a) meteorology conditions (air temperature, wind velocity etc.), b) type (various kinds of forest combustible materials) and their state (load, moisture etc.).