A method of calculating reflection high-energy electron diffraction intensities is developed within the framework of two-dimensional Bloch-wave approach. In the course of computations only wave-field-related quantities are employed (rather than transfer or scattering matrices). The intensities of reflected beams are calculated iteratively. The very good convergence of the method is demonstrated for Pt(111). For scattering systems with a large number of diffracted beams (exceeding 100\char21{}500) this iterative method is potentially faster than traditional direct methods. More importantly, a number of possible approximations can be easily derived on the basis of the iteration sequence introduced.