MagSaki(Tri) software was developed for the purpose of analyzing the magnetic data of trinuclear octahedral high-spin cobalt(II) complexes. The software enables analyses for five types of trinuclear cobalt(II) structures, including equilateral triangle shapes, isosceles triangle shapes, and linear shapes, to obtain magnetic parameters: the interaction parameters, J and J’, the spin-orbit coupling parameter, λ, the orbital reduction factor, κ, and the axial splitting parameter, Δ.