Polymer injection is an effective technique for increasing oil production in the later stage of petroleum exploitation. The plunger pump is the main equipment of this process. The ceramic plunger is usually used in the polymer pump instead of metal plunger due to its excellent wear-resistance and because it does not produce metal ions which could decrease the polymer viscosity. In this paper, the comparison is made theoretically and practically for the sintered ceramic material (Al2O3) and the plasma spray ceramic(Al2O3) plunger. The stress analysis is made using the finite element method and the field test is also carried out. Under real working conditions, the average working life reached 12,000 hours for plasma spray ceramic plungers, and about 6,000 hours for sintered ceramic plungers. The results show many advantages of plasma sprayed plungers over the sintered ceramic plungers.