Micro-mass sensors have important application in chemical and biological sensing. Based on the theory of thin film bulk acoustic resonator (FBAR), this paper represents four designs of different micro-mass sensor models. COMSOL Multiphysics™ software is used to simulate the FBAR sensor sensitivity, which with low-impedance acoustic layer and additional electrode frame. In the finate element simulation models, five different values of mass-loading were applied. From the experimental results, the characteristic parameters and the sensitivity of the FBAR sensors were obtained. It is known to us that the FBAR sensor’s frequency quality factor can be improved by using the electrode frame, and its sensitivity can be enhanced by using the low-impedance acoustic layer. To sum up, the above analysis shown that the best sensitivity is 1.351 × 10-12ng/μm2/Hz and the frequency quality factor is 1415, which is the FBAR sensor with a single-step electrode frame and a low-impedance acoustic layer.