Hybrid diesel multiple units (HDMU) are considered an effective way to reduce fuel consumption and pollution emissions in regional non-electrified railways. To minimize the fuel consumption of HDMU, this paper formulates an integrated optimization of driving strategy and energy management. By introducing convex relaxation and linearization, we propose a second-order cone programming method to solve this integrated optimization. Case studies of multiple scenarios validate the effectiveness and robustness of the proposed method. In addition, the simulation results show that compared with the sequential optimization with the step-by-step improvement of driving strategy and energy management, the integrated optimization considers the battery characteristics when optimizing the driving strategy and reduces the electric braking power of the train, thus allowing the battery to absorb more braking energy and reduce fuel consumption.