It is an interesting and practical problem to explore how to optimize the performance of quantum battery (QB) via quantum coherence.A QB model of a multi-level quantum system charged in a coherent auxiliary bath is constructed in this paper.Within the framework of collision model,the quantum master equation (QME) of QB charging in weak interaction regime is derived,and the solution of QME is obtained by the Ket-Bra entangled state method.Combining with numerical simulations,the influences of quantum coherence (the coherence magnitude and the coherence phases) on the maximal extractable work of QB are analyzed.It is revealed that quantum coherence,under certain conditions,can play the role of QB′s “fuel” to effectively improve the charging performance of QB.