The invention discloses a water sealing and stopping piston for a dynamic triaxial apparatus. The water sealing and stopping piston for the dynamic triaxial apparatus comprises an inner piston, an outer piston, a water stop rubber ring, a plurality of water sealing brushes and an excitation coil; the outer piston is arranged outside the inner piston in a sleeving mode; the outer wall of the outerpiston is provided with external thread grooves; the excitation coil is wound in the external thread grooves; the outer wall of the inner piston is provided with an internal thread groove; the inner wall of the water stop rubber ring is provided with a thread protrusion; the water stop rubber ring is arranged on the outer wall of the inner piston in a sleeving mode; the inner piston is tightly attached through matching of the thread protrusion and the internal thread groove; the multiple water sealing brushes are bonded on the outer wall of the water stop rubber ring; the water stop rubber ring comprises an inner rubber ring and an outer rubber ring; magnetorheological elastomers are arranged between the inner rubber ring and the outer rubber ring; the water sealing brushes are of a sheetstructure; and the magnetorheological elastomers are arranged inside the water sealing brushes. According to the water sealing and stopping piston, the water stopping effect is obviously, the abrasionresistance and the corrosion resistance can be effectively, especially a magnetorheological colloid is incorporated into the piston, the structural rigidity and the durability can be improved.