The pressure-composition-temperature(PCT) curves of $Mm_{0.6}Ml_{0.4}Ni_{5_x}Co_{x}(x{leqslant}2.5)$hydrogne stroage alloys(HSA) are determined and the mathermatical model of PCT curve the author proposed is applied to analyse the data of PCT curve of the alloy system. It been shown from the results that the PCT curve of $Mm_{0.6}Ml_{0.4}Ni_{5-x}Co_{x}$can also be modeled by the mathematical model and the calculated PCT curves are in good agreement with the experimental curves. A lot of physical parameters of these alloys which are very useful are estimated from the modeling.