Pomelo is an important fruit of citrus. The high fiber content of pomelo peel can be used as a good raw material to extract pomelo peel cellulose. Using pomelo peel cellulose (PP-C) as the raw material, the pomelo peel nanomicrocrystalline cellulose (PP-NCC) was prepared by sulfuric acid hydrolysis method. The micromorphology, aspect ratio, infrared spectrum, crystallinity, and thermal stability of the PP-NCC were analyzed. The effect of PP-NCC on the rheological properties of carboxymethyl starch filmforming fluid was studied. It was found that the PP-NCC was a rodshaped crystal with an aspect ratio of 8 to 20, and the proportion of aspect ratio greater than 10 was over 60%; the main substance of PP-NCC was cellulose; the crystallinity of PP-NCC was increased from 55.64% before acidolysis to 74.35%, and its initial thermal decomposition temperature was decreased from 240℃ to 212℃. PP-NCC could be used as the reinforcing agent of carboxymethyl starch film. According to the equation, the rheological index was less than 1, indicating that pomelo peel nanomicrocrystalline cellulose/carboxymethyl starch film forming fluid was pseudoplastic fluid. G′ of the film forming liquid was greater than G″, and no crossover occurred between the two within the frequency scanning range, showing that the composite film forming liquid was of weak gel structure. The viscosity coefficient KPL in static rheological parameters, the zero shear viscosity and the energy storage modulus in dynamic rheological parameters were positively correlated with the addition of nanocrystalline cellulose, showing that the dispersibility of PP-NCC in the filmforming liquid was good, which was helpful to strengthen the interaction of the internal structure of the filmforming liquid. The nanofilm of pomelo peel fiber showed better functional properties and can be used as a significant direction for comprehensive utilization of pomelo peel. 