The paper presents the application of Stochastic Kinetic Mean Field (SKMF) method for ordering of A$_{3}$B$_{1}$-type alloys. The synergy of both ordering and segregation in binary-alloy cubic nanoparticles is demonstrated. A simulation of size and diffusion-asymmetry effects on the ordering of binary alloy is performed. The dependence of the time delay of A$_{3}$B$_{1}$ phase ordering on the noise amplitude in SKMF method and dependence of order parameter on temperature at the absence of noise are found. Decomposition of the metastable solid solution with precipitation of the ordered A$_{3}$B$_{1}$ phase is studied at various noise amplitudes.