Computer algorithm of metameric color matching in subtractive color photography has been established using nonlinear optimization by Simplex technique. Suitable computer program has been developed for an IBM-1130 computer in Fortran IV language. Merits and Demerits of this technique are discussed in comparison with the Newton-Raphson approximation and the Regula-Falsi method. It has been elucidated that the Simplex technique is superior to the others especially when no feasible solution can be obtained by them.