The second-order integral model proposed by Yannopoulos (2006) for plane and round turbulent buoyant jets in stagnant and uniform environment is applied to a plane buoyant jet in a stratified ambient fluid. Initially, the partial differential equations for volume, momentum and tracer conservation are integrated on the cross-section of the buoyant jet, on the basis of assuming self-similarity. Closure is obtained by assuming a constant spreading rate of the buoyant jet up to the location of trapping. The complete system of the ordinary differential equations is solved by the aid of the fourth-order Runge-Kutta algorithm. In addition, an effort will be made for a fluid mechanics analysis of the phenomenon within the trapping region. The proposed model is validated in the region from the jet exit and up to the spreading layer by comparing the results with numerical data for a vertical plane buoyant jet (Yannopoulos 2006).