In order to achieve the purpose of rapid reinforcement of underwater concrete pier column of bridge without drainage, this paper proposed a strengthening method for underwater concrete pier column with Basalt FRP mould shell without drainage based on the concept of underwater self-stress undispersed concrete and “assembly type”. To study the axial compression performance of concrete pier columns by this strengthening method, eight specimens were made to carry out axial compression tests. The effects of Basalt FRP mould shell reinforcement, filled concrete performance, filling layer thickness and maintenance environment on the axial compression failure mode, bearing capacity and toughness of the specimens were studied. The test results show that Basalt FRP mould shell reinforcement could effectively improve the bearing capacity and toughness of the specimen；using underwater self-stress non-dispersive concrete as filling layer, adding proper amount of expansive agent, and controlling the strengthening thickness of the filling layer were beneficial to obtain better reinforcement effect. In freshwater environment, the ultimate bearing capacity of Basalt FRP mould shell strengthened specimen was better than that of seawater environment. According to the experimental results and some existing formulas of axial compressive bearing capacity of confined concrete columns, the formulas for calculating the axial compressive bearing capacity of concrete pier columns strengthened with Basalt FRP mould shells was proposed, and the theoretical calculation results were in good agreement with the experimental results.