The fitting methods of the exponential and polynomial curves are introduced in detail. 13 samples were indented on NANOINDENTER II, including 4 bulk and 9 film/substrate samples. The maximum indentation depths were set to two groups. The depths of one group were 200 nm and 500 nm respectively, while the depths of the other group were 1 μm and 2 μm respectively. 4 indentations were done on each sample under the presetting indentation depth group. 52 unloading load—displacement curve data files for 13 samples were obtained. All unloading curves were fitted using different curve fitting methods and their corresponding parameters were obtained. The hardness and elastic modulus values of all samples were evaluated using the parameters, and the relations between the unloading curves and the fitting curves were analyzed. The analysis results showed that 5th power polynomial curve fitting method is the best one among the 6 curve fitting methods, while the exponential curve fitting method is the worst. Since curve fitting methods may have much influence on the measuring results of the material mechanical properties using nanoindentation, so much attention should be paid to the precision analysis , the standardization of the measurement and evaluation of MEMS material’s mechanical properties using nanoindentation.