The experimental data of nitrogen oxides formation dynamic for the different fuels types burning in fluidized bed boiler, what has been burning at fluidized bed are presented. Under experiments has been shown, formation of nitrogen oxides are realized with two stages: with coke burning out process as well as volatiles combustion. Coke reminder nitrogen under oxidation process used similar heterogeneous mechanism as well as at carbon burning. Has been estimated it transformation degree to nitrogen oxidizes, what can be calculated with nitrogen oxidize and carbon reaction rate constant. Nitrogen oxidize release with volatilize burning process described with help total balanced reaction. Mechanisms of nitrogen oxidized realization at the different stages of fuel particles burning process resulted to set of the calculation method of NO X outlet from particles in dependences of fluidized bed furnace height.