Mixing SiO_x materials with graphite materials has become a key technology to improve their performance, but it is still unclear what kind of graphite materials help to construct a stable electrode structure. The purpose of this study is to explore the effect of graphite morphology on the structure and performance of SiO_x/C composite electrodes (850 mAh g⁻¹). For the SiO_x/C59 composite electrode constructed by the lamellar graphite (C59) with a big aspect ratio and SiO_x particles, the SiO_x particles agglomerate in the pores of C59 particles. This uneven electrode structure could lead to excessive stress and strain of the electrode during cycling, which causes the anode electrode structure failure and cycling performance deterioration. While the small-size lamellar graphite (SFG15) with random orientation helps to construct stable electrode structure with uniform particle distribution and pore structure, which could reduce the stress and strain change of the electrode during cycling. Thus, the composite electrode (SiO_x/SFG15) exhibits better cycling performance compared with SiO_x/C59 composite electrode. This work reveals the structure-activity relationship of graphite morphology, electrode structure and the mechanical and electrochemical performance of the electrode, and provides a guide to the design and development of the high capacity SiO_x/C composite electrode structure.