An out-of-plane elastic vibration test method is developed to directly study the elastic stability of elastic Ti foil-supported porous carbon nanocomposite (CNC) counter electrode (CE) of dye sensitized solar cells (DSSCs). The stability of CE, estimated by that of power conversion efficiency (PCE) of the CE-based DSSC device, is studied from the views of CNC morphology, equivalent resistances, exchange current density and contact model of CE. The results suggest thinner thickness and bigger interbundling degree of CNC layer is beneficial to the total internal impedance value of CE, and then beneficial to the CE stability. With optimal CNC structure, even if the CE is springed 1000 times with max amplification about 10 mm, the PCE of CE-based DSSC can remain 80% of the initial value. The test method is interesting and the results may have a potential use for elastic stability study of general elastic devices.