In this paper, a method is presented to determine the effects of Vlasov nonuniform torsion caused by horizontal loads on structural systems of tall buildings. In this method, a realistic assumption is made that the variable horizontal loads act at each story level instead of a uniform lateral load along the height of building. For the presented method, an algorithm is prepared in software MATHCAD in which the cross-sectional characteristics are calculated and the sectorial coordinate diagram is plotted. The results can be obtained in a short time, hence it is not needed to solve the time consuming differential equations. The method is compared with the studies of Taranath and Smith & Coul, and is also compared with the softwares ANSYS and CONSTEEL by modeling as a cantilever beam to check the accuracy of the algorithm.