This paper reports modeling and design of AlN piezoelectric microcantilevers for operation in liquid environments. Microcantilever sensors demonstrates high sensitivity and measurement resolution for rheological properties analysis and biological event detection while used in liquid media. However, a hydrodynamic force induced by a liquid causes a damping effect on a microcantilever, and such damping directly impacts the dynamic response of a microcantilever. This is related on the performance of the microcantilever sensor. To develop AlN piezoelectric microcantilevers for in-liquid application, it is necessary to simulate various cantilever dimensions and find the optimal design. In addition, the impact of various liquid properties (i.e. viscosity, density, specific heat, etc.) on the cantilever operation should be fully understood. To find the optimal design of the AlN piezoelectric microcantilever sensor, the methods of analytical and numerical modeling were used. For simulation, COMSOL Multiphysics 5.3 Fluid-Structure Interaction study was used. To validate our microcantilever-liquid interaction modeling, we compared the simulation and experiment results of silicon AFM cantilevers with various dimensions in different liquid media. The validated modeling and simulation methods will be applied to develop AlN piezoelectric cantilevers with multiple vibration mode (transverse, contour, and thickness-modes) for various in-liquid application areas.