Abstract: CNG tanks have the potential risk of physical explosion. In order to study the dynamic crack propagation characteristics of CNG tanks during physical explosion, a numerical analysis model of fluid-solid coupling was established based on the thermo-viscoplastic constitutive model, J-C failure criterion and penalty method contact algorithm. In this way, the crack propagation characteristics of CNG tanks and the release rules of high-pressure natural gas were analyzed. The results show that the tank cracks tend to propagate along the axial direction under physical explosion at a speed up to 200 m/s to 300 m/s, and the crack propagation is incremental without any dominant frequency. Besides, the reaction force generated by the rapid release of high-pressure natural gas can lead to the axial bending deformation of tanks. Moreover, the two ends of tanks are still under high internal pressure when crack propagation ends, and the energy of crack propagation is only provided by partial compressed natural gas. Generally, the research results have positive significance to the analysis and inversion of the physical explosion accident of CNG tanks.