To address the severe overreading issue in two-phase vortex-street wet gas measurement, this paper proposes an overreading correction and online phase flow measurement method for wet gas based on the dual-mode detection of vortex shedding and disturbance wave height. First, a ring-shaped liquid film parameter sensor was constructed based on the conductance method, followed by an equivalent optimization design and calibration. Subsequently, full-scale flow experiments were conducted on an adjustable-pressure wet gas annular-mist flow test rig based on atomization mixing. To ensure the stable evolution of the flow pattern under extremely low liquid hold-up conditions, an impingement-type PJ10 high-pressure atomizing nozzle was coaxially installed at the top of the mixing section. The experiments covered a wide range of carrier gas conditions and liquid flow rates. By applying a dual-threshold method to the liquid film thickness signals to distinguish disturbance waves from ripples, the disturbance wave height was accurately extracted and cross-validated. The gas-phase Weber number and liquid-phase Reynolds number were selected as the dimensionless parameters characterizing the high-speed gas shear and the viscous dissipation of the liquid film, respectively, to establish correlation equations for the disturbance wave height and the vortex overreading factor. Finally, a wet gas phase flow measurement model based on an iterative solution approach was proposed, with the iteration convergence threshold set to 0.1%. This algorithm achieves rapid and stable convergence within only a few iterations. The results demonstrate that, after correction, the maximum error of the gas-phase volume flow rate is reduced from 12.1% to within ±1.0%, with a prediction uncertainty of 0.61%. For the liquid-phase volume flow rate, 96.2% of the test points are controlled within a full scale percentage error of ±15%, with a prediction uncertainty of 6.52%. By deeply utilizing the internal flow information (disturbance wave height) of the annular-mist flow for overreading correction, the proposed model overcomes the limitations of traditional methods and offers the significant advantages of simple modeling and excellent real-time performance for online monitoring.