5,10-Dimethylphenazine (DMP) is a recently reported high-performance organic electrode material, however, its high solubility in electrolyte solution is responsible for the capacity decay during cycling. Poly(2-vinyl-5,10-dimethyl- phenazine) (PVDMP), containing DMP as active groups, shows limited solubility in electrolytes, whereas the impact of its molecular weight on the electrochemical properties has not been well investigated. Here, PVDMPs with two molecular weights, PVDMP-2K (M_w=2300 g•mol^－1) and PVDMP-12K (M_w=12000 g•mol^－1) were prepared. Cyclic voltammetry (CV) characterization shows that the peak current (i_p) increased linearly with the concentration of PVDMP at low concentrations, while at high concentrations, there was a poor linear relationship between i_p and M_w. This result demonstrated that the molecular weight of PVDMP affected its electrochemical behaviors. From the morphology investigation, it can be seen that PVDMP presented spherical aggregates with different diameters in solution and the diameter is increased with the molecular weight of PVDMP. Therefore, this spherical aggregate could influence the diffusion efficiency of PVDMP during the electrochemical reaction and the utilization of the active groups, and thus demonstrated different electrochemical behavior.