NaV2O5, possessing robust, open and large-space layered crystal structure, was recently found as one novel promising intercalation-type high-capacity anode material for Na-ion batteries. To address its difficult issue of morphology control for conventional solid-state method, our group proposed previously a two-step hydrothermal method to controllably synthesize a well-crystallized NaV2O5 mesocrystal. However, this two-step method was still time-costing and a bit complex. In order to further promote its further research development and industrial application, it remains a huge and attractive challenge to explore a simple and time-saving method to synthesize promising NaV2O5. Herein, we propose a facile one-step hydrothermal strategy to realize the short-time synthesis of 3D bundle-like NaV2O5 mesocrystal. In this simple one-step method, sodium oxalate (Na2C2O4) is tactfully designed as simultaneously reducing reagent and Na resource, so that its synthesis time is greatly shortened more than 5 times. Furthermore, the crystal growth mechanism of NaV2O5 mesocrystal is also revealed. Amazingly, the ex-situ XRD measurement reveals that the electrochemical intercalation/deintercalations are reversible and the crystal structure of NaV2O5 is stable. So, NaV2O5 mesocrystal prepared by one-step method exhibit the promising electrochemical performance, and its reversible capacity is up to 360 mAh/g.