The invention discloses a metal oxide MEMS gas sensing chip based on a secific morphology and a size grading structure and a manufacture method thereof. The method comprises the following steps: 1) preparing a metal oxide sensitive material having the specific morphology and size; 2) mixing the prepared sensitive material obtained in the step 1) and nano-level metal oxide, adding precious metal toobtain the doped grading-structure sensitive material; 3) mixing the prepared grading sensitive material and a solvent, a wetting agent, a dispersant, a surfactant, and a pH conditioning agent, stirring a mixture and defoaming the mixture to obtain an uniformly dispersed multi-component slurry; and 4) spraying the prepared slurry on a MEMS micro-heating plate, and performing low-temperature and high-temperature treatment to form an uniform and sensitive membrane layer to manufacture the MEMS gas sensing chip. The grading-structure sensitive material has the advantages of high sensitivity andbatch synthesis; the formed sensitive membrane layer is stable and uniform, and has the advantages of good consistency and less material amount; the MEMS gas sensing chip has high response on VOCs, and is expected to be widely used in intelligent household, medical application, cell phone and bracelet.