Abstract: Applying our boundary theory of phase diagram, when the limited data are available, the multicomponent phase diagram can be constructed. H. Gupta constructed the multicomponent phase diagram by overlapping ZPF lines. By our method, it can be done more simply and directly, and the case which can not be treated by H. Gupta's method theoretically can be dealt with.

Key words: Horizontal section at constant temperature, Boundary theory of phase diagram, Construction of phase diagram