In this research a new high resolution voltage-to-frequency type converter and measurement system for the differential signals of CMOS-MEMS sensor is proposed. In order to verify the feasibility of high resolution converting, a two-dimensional thermoelectric flow sensor with quadrant symmetrical structure was fabricated by using 2P4M 0.35μm CMOS-MEMS process of TSMC. The measurement circuit is designed by using Gated-Ring-Oscillator (GRO) structure to convert the output voltages of CMOS-MEMS sensor to the frequency signal. For the differential type signals, each output of two signals will be delivered to two GRO and each ring gives a corresponding oscillation frequency with small difference. Based on the heterodyne conversion architecture, after a low-pass filter, the output of mixed high frequency signals gives a low frequency with high-precision resolution of conversion. Beyond the traditional complex analog signal processing circuits, the proposed converter and measurement system gives a new approach to reach higher resolution highly-integration for the CMOS-MEMS sensor's applications.