The grand challenge in the development of Platinum (Pt)-based electrocatalytic hydrogen evolution reaction (HER) catalyst is their high-cost, low utilization and less controllable, limiting its wide application in hydrogen economy field. Therefore, exploring a new technique to construct catalyst require minimal amounts of Pt and maintain high performance is very necessary. Herein, we first designed a high-efficiency electrocatalyst based ultralow Pt loading (1.27 μg cm‒2) on two-dimensional Ti3C2Tx MXene support by controlling Cu monolayer underpotential deposition (UPD), and then galvanic replacement Cu monolayer with Pt. Due to the energetically favorable metal-support interaction, in acidic media the as-prepared Pt-Ti3C2Tx MXene catalyst achieved a current density of 10 mA cm‒2 at low overpotential of 30 mV. Furthermore, the Pt-Ti3C2Tx MXene catalyst also exhibited a superior HER activity with high turnover frequency (TOF) of 41.8 s‒1 and mass activity of 41.3 A mgPt–1, which were about nearly 47 times those of commercial 20 wt% Pt/C catalyst, respectively. This work demonstrate the potential of Ti3C2Tx MXene as support for design of ultralow Pt loading electrocatalyst through Cu UPD-Galvanic replacement method that can be used for a wide range of catalytic reaction.