The invention discloses a method for quickened extraction of wave energy based on compressible fluid. Along with fluctuation of wave and under the driving of a sea level floating platform, seawater flows from openings at the upper and lower ends of a housing case of the two-way water turbine into the housing case through movement of a water turbine in a deep sea stable region in the perpendicular direction, and passes through an annular passage which is gradually narrowed and arranged between the housing case and upper and lower shrinkage bodies which serve as stators; the radius R of the opening of the housing case is larger than or equal to 0.3 m and less than or equal to 15 m; and sea water is compressed according to the ratio of the root radius r0 of the upper and lower shrinkage bodies to the centre radius r of a one-way rotary rotor, and the ratio ranges from 0.8-0.99. The invention also discloses a two-way water turbine realizing the method. According to the invention, the overflowing area of sea water in the housing case is greatly reduced, the speed for impacting the one-way rotary rotor by the fluid is greatly improved, and the rotating torque of the one-way rotary rotor is increased. Within the parameter range, the output power of the water turbine is improved, and the generating power of a generator is further improved.