Porous carbons with controlled pore structure have attracted great interest owing to their excellent application potential. Herein, we report a simple synthetic route to synthesize the core-shell C@SiO2 spheres with various pore structures by calcining core-shell structured RF@SiO2 (RF = resorcinol-formaldehyde resin). The obtained C@SiO2 spheres had high surface areas (238.5–732.5 m2/g), large pore volume (0.111–0.647 cm3/g) and abundant micro-mesoporous structure. The mesopore size of C@SiO2 spheres can be easily turned in the range of 8–15 nm, by simply modifying the carbonization temperature, size and heating rate of RF@SiO2 spheres. Among these, S–C@SiO2-400 spheres had higher mesopore volume of 0.207 cm3/g, this was related to internal carbon slices structure. Meantime, the toluene adsorption capacity of S–C@SiO2-400 spheres could reach 448.2 mg/g, which increased by 88.73% compared to ordinary carbon spheres. Moreover, the formation mechanism of the mesopore carbon slices structure was evaluated based on controlled experiments. This work provides a new synthetic method of micro-mesoporous carbon spheres, which can further enrich the application of carbon materials.