An iteration method for the solution of the problems of cosmic ray (CR) propagation in heliosphere is proposed. The method is based on the smallness of the anisotropy degree of cosmic rays. As zeroth approximation, CR density satisfying the equality of CR stream in heliosphere to zero is used. The next iterations are built based on CR propagation equation written in canonic form. The CR density calculated for a problem accepting the exact analytical solution are compared with one obtained by the iteration method. The another form of CR propagation boundary problem for the stationary spherical-symmetrical case is derived.