We revealed the electrochemical evolution process and clarified the vital factors that affect the cycling stability of micro-nano assembled MnCO3 through systematical characterizations such as SEM, TEM, HRTEM, XRD pattern, EIS plots, charge-discharge profiles and CV curves. We found that the specific surface area and the amount of effective active materials determined the electrochemical performance together. Particles with large specific surface area have better original capacity but more probability of collapse resulting in the loss of effective active materials. How the collapse happens decides the loss of effective active materials as well as the decline rate of capacity. Inspired by these understandings, we introduced electrochemical inert materials, CaCO3 as an example, to constrict the collapse and keep the secondary morphology for improving cycling stability. The strategy is proved to be effective by the formation of Ca0.1Mn0.9CO3, which can still deliver an excellent reversible capacity of 568.3 mA h g(-1) in the 1000th cycle at the rate of 5 C. It provides us a new way to deal with the large volume changes of conversion-reaction materials.