The mesocarbon microbeads (MCMBs) were prepared from the aromatic-rich heavy oil of a refinery via heterogeneous nucleation thermal polycondensation. The effects of reaction temperature, pressure, time and amount of additive on the yields, morphology and particle size distribution of MCMBs were investigated. And the electrochemical performance of MCMBs with different structures was characterized as well. The results demonstrate that with the increase of reaction temperature, the extension of reaction time and the decrease of reaction pressure, the content of mesophase spheres in the polycondensation product increases, and a noticeable coalescence between spheres occurs. The average particle size of separated green MCMBs shows a gradual increase. With the increase of the addition amount of nucleating agent, the content of mesophase spheres in the polycondensation product increases significantly without coalescence phenomenon. And the average particle size of green MCMBs firstly rises and then falls. Under the optimal reaction conditions, the yield of green MCMBs reaches 32.27%, with the most uniform particle size distribution. The carbonized MCMBs exhibits the first-cycle Coulomb efficiency amounts of 64.1%, and its specific capacity remains stable at 408.5 mA·h/g after 100 cycles.