Abstract: An urban ground noise field is made up of natural ground noise and cultural ground noise with different temporal and spatial distribution characteristics. In general, the natural ground noise satisfies three features of consistency, stability, and correlation with cultural ground noise appearing as non conformance, instability, and non correlation. Referring to their different characteristics, this paper proposed three principles on the urban ground noise separation and presents a improved method of multivariate separation to effectively separate the two types of noisy fields. We tested four types of standard signals and the results demonstrated superiority of multivariate separation. In addition, exploratory experiments in Shenzhen indicate that the proposed method of multivariate separation can divide urban ground noise signal effectively into two parts, and can be refined underground geological information. By separating the underground noise, we can quantitatively compare the noise level of natural ground noise and cultural ground noise.