Abstract: The decrees for pardon that are written before and in early Tang Dynasty mainly act as judicature. The decrees for pardon that are delivered during Wu Zetian's rule begin to experience great changes. Besides the function of judicature in Tang Dynasty, the function of legislation has been added to decree for pardon. This change happens when Wu Zetian's power rises to a historical height. The legislation function of decree for pardon continues to exist thereafter, consisting of a unique feature of Tang decree for pardon.