Many research groups have studied tissue engineering techniques for solve the limited use of donated lungs and immuno-rejection after organ transplantation. The most promising method for lung cultivation is the use of bio-scaffolds prepared by removing cells from organ harvested from human donors or other animals. In this study, 12-13 weeks old rat lungs were decellularized and the fluid mechanic impedance of the lungs was measured. The purpose of this study is to analyze the degree of decellularized of organ by measuring and analyzing the fluid mechanic impedance of the lung which changes with decellularizing. The fluid mechanic impedance of the lung was calculated by applying a single frequency analysis to the flow rate and pressure of the perfusion solution. During the decellularization, the impedance was measured and the phase decreased as the experiment proceeded. Measuring the fluid mechanic impedance and phase during decellularization is expected to detect internal changes in the invisible organ.