Two kinds of new macro-ate-initiator (MAI) having dual decomposition temperatures were synthesized by polycondensation between 4,4’-azobis-4-cyanopentanoyl chloride (ACPC) and 2,2’-azobis-2-cyanopentanol (ACPO) (MAI [2A]), and between ACPC and 2,2’-azobis 2-methyl-N-2-hydroxyethylpropionamide (AHPA) (MAI[2B]). MAI [2A] and [2B] were compared with MAI [1] having a single decomposition temperature synthesized by polycondensation between ACPC and bisphenol-Z. Two step polymerization of styrene and methyl methacrylate initiated with MAI [1], [2A], and [2B] was carried out. It was confirmed that the new MAI [2A] and [2B] initiated effectively at each step of polymerization due to their dual decomposability, resulting in higher conversion of the comonomers to yield block copolymers than the case initiated with MAI [1].