Governing equation for describing the probe-dynamics of amplitude-modulation AFM and the mechanism of probe-to-sample interaction were formulated to develop a method for analyzing the elasticity of soft samples. This method features in combining the harmonic oscillation of the tapping probe, the surface energy, and the contact mechanics of the probe-to-sample interface with Derjaguin- Muller- Toporov model. Six PC-12 neuron-like cells were employed to test applicability of the method. The experiment results revealed that the Young’s moduli of the scanned cells are consistent with the literature in order of magnitude. Using the proposed method, we could obtain the topography and global distribution of elasticity of live cells in just one scan which is more efficient than the local indentation-test with AFM.