N⁶-methyladenosine (m⁶A) is one of the most abundant messenger RNAs modification. Increasing evidence illustrates its critical role on gastric cancer. Here, present research focuses on the potential function of m⁶A methyltransferase Wilms’ tumour 1-associated protein (WTAP) in gastric cancer tumorigenesis. Firstly, m⁶A immunoprecipitation sequencing analysis (MeRIP-Seq) analysis demonstrated the m⁶A profile in gastric cancer cells. Both WTAP and the m⁶A expression were up-regulated in gastric cancer tissue and cells. The high-expression of WTAP was closely correlated with poor prognosis of gastric cancer patients. Functional experiments illustrated that WTAP promoted the proliferation and glycolytic capacity (glucose uptake, lactate production and extracellular acidification rate) in vitro, and the knockdown of WTAP suppressed the tumor growth in vivo. Mechanistically, HK2 was identified to be the target of WTAP using MeRIP-Seq and MeRIP-qPCR. WTAP enhanced the stability of HK2 mRNA through binding with the 3’-UTR m⁶A site. In conclusion, our results demonstrate the oncogenic role of WTAP and its m⁶A-mediated regulation on gastric cancer Warburg effect, providing a novel approach and therapeutic target in gastric cancer.