The integration of mesoporous silica materials (MSMs) and metal organic frameworks (MOFs) has garnered significant attention. To date, various strategies have been developed to synthesize MSM-MOF composites. However, it is challenging to synthesize MSM-MOF with high MOF contents (e.g., metal to silica molar ratio above 0.4) and well maintained mesopores. Here, we report a metal oxide conversion strategy for the synthesis of dendritic mesoporous silica nanoparticles (DMSNs)-MOF nanocomposites with a high MOF content, using zinc-based MOFs as examples. By adjusting the amount of zinc salts and the reaction time, DMSN-ZIF-8 can be prepared with a zinc to silicon molar ratio up to 0.4-0.8:1, and the mesopores can be reserved at the zinc to silicon ratio of 0.4. This strategy can be further applied to synthesize DMSN-ZIF-90 nanocomposites. This work has provided a robust strategy for the synthesis of MSM-MOF composites with adjustable compositions and nanostructures.