[en] Algorithm of operative solution of the P₁-equation system of the method of spherical harmonics for cylindrical two-dimensial shield compositions has been developed and realized in the program. The algorithm is intended to be included into the system of program complex shield calculation according to techniques, combining succession application of discrete ordinate method and P₁-approximation. The algorithm is oriented to solution of the problems with preliminary axial radiation propagation at rather small gradients of solution with respect to radial variable. Difference analogues of P₁-equations were obtained under the assumption of exponential solution dependence on axial variable. The system of nonlinear finite-difference equations is solved with the use of effective technique, lying in successive application of h-factorization and parabolic runs. Independent algorithm testing, which demonstrated quick convergency of calculation process for a wide range of model problems, was conducted