Abstract: The pre-observation design and optimal observation mode selection are the prerequisites for nuclear magnetic resonance (NMR) logging data acquisition. Different NMR observation modes correspond to different echo acquisition sequences, and the measurement results have an important impact on the understanding of NMR responses of reservoirs and the accuracy of reservoir evaluation. In this study, the gas-bearing carbonate reservoir in the Ordovician Majiagou Formation in the eastern Ordos Basin was taken as the research object. NMR logging data of different observation modes was used to analyze the applicability of four observation modes including B-Expert, GAS2D712, BRAZIL09, and OKIE12 by comparing relative error and coincidence rate from two aspects: porosity and fluid identification. The results show that in terms of porosity, the NMR-based porosity inverted by the B-Expert mode using collected echo exhibits the highest accuracy. After light hydrocarbon correction, the accuracy of NMR-based porosity inverted by the GAS2D712 and OKIE12 modes demonstrates a notable enhancement. In terms of fluid identification, the GAS2D712 mode presents a distinct advantage, with a higher coincidence rate of fluid identification compared to the BRAZIL09 and OKIE12 modes. Therefore, the GAS2D712 mode can not only ensure the accuracy of porosity calculation but also have a high coincidence rate of fluid identification, and it can be used as the main mode for NMR logging acquisition in the study area. This study can also provide a reference for the optimal NMR observation mode selection and data acquisition in other study areas.