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We execute a detailed spectral-timing study of Cygnus X-1 in the low/hard,intermediate and high/soft states with the Hard X-ray Modulation Telescopeobservations. The broad band energy spectra fit well with the "truncated diskmodel" with the inner boundary of the accretion disk stays within $\sim$10\textit R$_{\rm g}$ and moves inward as the source softens. Through studying ofPDS, rms and Fourier-frequency component resolved spectroscopy, we find thatthe X-ray variations are generated in two different regions for each state. Wediscover that the major role that contributes to the X-ray variation is the hotcorona rather than the accretion disk. We suggest a scenario with differentcorona geometry for each state based on the truncated disk geometry in whichthe corona wraps up the disk to form a sandwich geometry in the low/hard state,and then gradually moves away from the disk in direction that is perpendicularto the disk until forming a jet-like geometry in the high/soft state.

Evolution of Accretion Modes between Spectral States Inferred from Spectral and Timing Analysis of Cygnus X-1 with Insight-HXMT observations