A high-resolution optical vector analysis (OVA) based on optical single sideband (OSSB) modulation using a dual port Mach–Zehnder modulator (DP-MZM) is proposed and demonstrated. By using the DP-MZM, an OSSB modulation signal is generated. The generated OSSB signal is propagating through the device under test (DUT). After the optical-to-electrical conversion in photodetector (PD), a photocurrent carrying the frequency responses of the DUT is obtained. After signal processing, the photocurrent corresponding to the frequency component is extracted, and the frequency responses of DUT are measured with high-resolution in simulation. To eliminate the frequency response of the system, a calibration procedure is performed by removing the DUT. Compared to the traditional methods, the proposed OVA can be used to measure the frequency responses of high-quality optical devices with MHz-resolution over a large measurement range. By using the DP-MZM, the stability is improved, and the complexity is reduced. The proposed method is theoretically analyzed and verified by simulation. A simulation for measuring the frequency responses of the ideal phase-shifted fiber Bragg grating and the ideal Fabry–Perot cavity is carried out, the frequency responses in a range of 50 GHz are measured with a resolution of 1 MHz. The proposed method can be potentially applied in the field of characterization of integrated optoelectronic devices and future photonic systems.