It has been found through phase diagram analysis that the low-pressure metamorphic belt of Erlangping Group is a superimposed metamorphic belt. During the uplift of middle-pressure metamorphism, the low-pressure metamorphism took place. pT conditions of middle-pressure metamorhpism are 0.5～0.6 Gpa and 560～580℃. The pressure of low-pressure metamorphism is 0.3～0.45 GPa, and the temperatures of the andalusite-staurolite zone and the cordierite zone are 510～580℃ and 590～620℃, respectively. The pTpseudosection is a powerful tool for analyzing the pT evolutionary process and pT conditions when there exist several mineral assemblages formed in different periods and under different conditions.