As a core component of in-vitro coagulation sensor structure, the sensor failure is easily caused by the deformation of its elastic support. To address this issue, this paper proposes a reliability life assessment method, which is based on the fatigue life and breakage mode of the sensor. Failure analysis is performed on the sensor reliability according to the operating principle and structural features of the in-vitro coagulation sensor. By formulating the mechanical model for theoretical reliability analysis, the expression of determination criterion for the life limit of coagulation sensor is derived, which is attributable to the strain transfer coefficient of elastic support. The harmonic response of the elastic support is analyzed by the finite element analysis. An elastic support-based method for assessing the ultimate sensing life is proposed by taking the 15th level of sensor fatigue life as the failure threshold. By using this method, 108 million stress fatigue tests are implemented on the dual-channel in-vitro coagulation sensor. The full-scale relative effective errors of spiral clips for the elastic support are 3. 89% , 3. 79% and 4. 75% , respectively. Under the 4. 5% boundary of the full-scale relative effective error, the results indicate that a clip has reached its stress life limit, while other two clips are yet to reach the safety threshold level. Thus, the fatigue life reliability of the sensor is approximately 108 million times, which basically agrees with the simulation data. These results verify that the proposed life limit assessment method for the in-vitro coagulation sensor conforms to the requirements of sensor failure analysis, which also offers a core technique for improving the development procedure of such sensors.