The process of a two-staged ion heating of counter streaming plasma flows under a rapidly increasing magnetic field is studied by measuring plasma parameters and changes of fields. In the early stage of the compression, ions of the initial plasma are heated up to 300∼400 eV till 240 ns by the reflected ions from the magnetic piston existing near the wall. By a stable and strong azimuthal current sheet around the plasma column existed already in the encounter process, a large magnetic well is formed after 240 ns. By the interaction with this moving magnetic barrier, ions are accelerated effectively and the ion temperature reaches 3∼4 keV at last. The density and the temperature of electrons are (2∼3)×10 15 cm -3 and 300 eV, respectively.