The seismic interferometry is a microtremor survey algorithm for achieving the dispersion curve between two geophones. To obtain the dispersion curve, the traditional seismic interferometry in the frequency domain uses monotonically decreasing Bessel functions to fit the coherence coefficients. The effective dispersion points of calculation are less, and high frequencies are missing. To perform microtremor detection, the resolution of shallow structure is low, and there are exploration blind areas with a depth similar to the station distance. An improved seismic interferometry method is proposed, which uses the signal-to-noise ratio model of the measured signal to correct the coherence coefficients of two signals. The coherence coefficients are divided into different intervals by the monotonicity of the first type of zero-order Bessel curve. Piecewise fitting Bessel function is utilized to solve the surface wave phase velocity. The engineering practice shows that this method has a good detection effectiveness. The high frequency band is expanded, and the detection accuracy is improved. The problem of shallow exploration blind areas is effectively addressed.