Thin films of TNPPcZn (Tetra-neopentoxy phthalocyanine Zinc) were spin-coated onto glass substrates. Studies on the changes of TNPPcZn aggregate have been made by using films annealed at various temperature. The XRD patterns and absorption spectra over the wavelength range of 500～800 nm were measured. With the increasing temperature, monomer of TNPPcZn was transformed into aggregate gradually. But when the temperature was upto 450℃, aggregate was changed to monomer again. At the same time, phase changes occurred from amorphous to crystal then to amorphous again.