The utility model relates to a moisture measuring system based on a differential pressure and rotational flow split-phase capacitance moisture content sensor. The device comprises a differential pressure flow meter and a moisture content sensor which are fixed on a measuring pipeline, the differential pressure flow meter and the moisture content sensor are horizontally mounted, incoming flow firstly passes through the differential pressure flow meter to measure the total virtual high-mass flow of two-phase flow, and then passes through the moisture content sensor to measure the liquid phase content in the two-phase flow, so that non-separation metering of the two-phase flow is realized; the moisture content sensor is a rotational flow split-phase capacitance moisture content sensor and comprises a rotational flow split-phase section and a capacitance measuring section, and the rotational flow split-phase section comprises a spiral blade supporting rod, two or more spiral blades distributed on the periphery of the spiral blade supporting rod and an outer pipe wall; the capacitance measuring section comprises a metal inner core, an insulating layer covering the periphery of the metalinner core and an outer metal pipe wall. The device is suitable for industrial on-site measurement and has high measurement precision.