Propellant materials are occasionally experiencing severe dynamic loading during transporting and service process, thus their mechanical characteristics and potential mechanisms under transient loading are needed thoroughly understanding for its integrity designing and reliable service. The paper focuses on the mechanical behaviors of propellant CMDB, along with its potential mechanism and constitutive characterizations. Mechanical behaviors are firstly studied experimentally under strain rates from 0.0001 s−1 to 3800 s−1 using Instron mechanical device and Hopkinson bar apparatus. Strain-controlled experiments are also performed for specific focus on severe multiple loadings. It is found that CMDB presents high rate-dependence, and shares parallel mechanical behaviors under wide strain rates. So does the strain hardening ratio. The microstructural observation on crack maps demonstrates that the crack is rate-dependent too, which presents the increasing dimension and decreasing quantity with increasing strain rate. The mechanisms are accordingly proposed based on microstructures, which can explain reasonably the rate dependences. Finally, a constitutive equation is succinctly deduced to well capture the mechanic characteristics at large deformation under wide strain rate range, and the involved less parameters own the overwhelming merit in engineering simulation and applications.