The invention relates to a thin film structure reducing laser direct-write photoetching point or line width and the preparing method. And the thin film structure comprises inorganic phase-transition thin film layer and buffer layer, where the inorganic phase transition thin film layer is composed of AgInSbTe or GeSbTe or SbTe, the buffer layer is made of high heat conductivity metal or semiconductor. And the thin film structure is made by DC magnetic controlled sputtering process and has advantages of simple structure, process easy to control, low substrate requirements, etc. and the test proves that it can obviously reduce the size of laser direct-write photoetching point and line width.