Dynamic analysis and study of Atomic force microscope in liquid environment is the main goal of this research. Hydrodynamic and squeeze forces act on Cantilever of Atomic force microscope which works in liquid environment, so. In this paper the effect of different environmental and physical factors had studied on frequency response diagrams. The importance of frequency response analysis is studying the possibility of occur a phenomenon which causes disturbance and decreases accuracy of imaging. Timoshenko beam model and finite element method had been used in order to simulation. Meanwhile interaction forces between sample and tip point in gas and liquid environment were also considered in simulations. Achieved results had showed that in comparison with gas, resonance frequency has decreased considerably in liquid environment which is due to additional mass of liquid and also amplitude is decreased in liquid environment that’s because of additional damping due to presence of liquid. Meanwhile several studies in repulsion and attraction area with more and less distance from equilibrium distance, had showed that in repulsion state, stimulation frequency is more than attraction area, that the reason is related to more hardness in repulsion area, and also the presence of interaction forces had caused that in zero excitation frequency, amplitude isn’t zero.