The Inertial Cavitation (IC) activity of Ultrasound Contrast Agents (UCAs) plays an important role in the developments and improvements of ultrasound diagnostic and therapeutic applications. However, various imaging methods and therapeutic applications have different requirements for IC characteristics. In the present work, both experimental measurements and numerical analyses were performed to investigate the IC thresholds of two commercialized UCAs, albumin-shelled KangRun® microbubbles approved in China and lipid-shelled SonoVue® microbubbles approved in USA, Europe and China. The IC thresholds of these two UCAs were measured at varied acoustic pulse lengths and bubble concentrations, according to the IC dose quantifications based on Passive Cavitation Detection (PCD). Then, the shell properties (shell elastic and viscous parameters) of UCAs were estimated by fitting the measured acoustic attenuation data using the coated-microbubble dynamic model. Finally, the influences of acoustic pulse length and UCA shell properties on the microbubble nonlinear behaviors were discussed based on numerical simulations, which would give us better understanding of the dependence of microbubble IC threshold on the sonication condition and physical structure properties of the coating shells. The experimental results show that: (1) the IC threshold of UCAs is dependent on the acoustic driving conditions (e.g., pulse length), the shell properties of UCAs and the bubble concentration; (2) for both the lipid- and albumin-shelled UCAs, the IC threshold generally decreases with the increasing UCA volume concentration; (3) IC threshold is observed higher for short-pulse excitation (e.g., 5-cycle pulse length), then its value decreases as the acoustic pulse length increases from 5 cycles to 20 cycles and finally tends to reach a steady state for even longer pulsed exposures; and (4) the shell interfacial tension and dilatational viscosity estimated for SonoVue® are smaller than those of KangRun®, which might result in lower IC threshold for SonoVue®. The results of current studies will be helpful for selecting and utilizing commercialized UCAs for specific clinic applications, while minimizing undesired IC-induced bio-effects.