The invention provides a forced-closing-and-opening two-stage functional plunger. The plunger comprises an upper pull rod and a lower pull rod. A first connecting part is connected to the top end of the upper pull rod. An upper plunger body is coaxially arranged on the outer layer of the middle of the upper pull rod. A first oil outlet valve bonnet and a first oil inlet valve bonnet are fixedly connected to the upper end and the lower end of the upper plunder body correspondingly. The first oil inlet valve bonnet is connected with a first support through threads, and a first annular groove is reserved. A first valve set is mounted in the first groove. A first valve ball is coaxially arranged at the lower end of the first valve seat and the outer layer of the upper pull rod. The forced-closing-and-opening two-stage functional plunger is provided with a first-stage plunger body and a second-stage plunger body, the first-stage plunger bears the whole liquid column load, the second-stage plunger body is used for sealing a whole liquid column above the plunger body and prevents leakage, and thus the leakproofness of the whole plunger assembly is ensured; and the plunger can be suitable for an oil well pump which can adapt to heavy oil wells, highly-deviated wells and gas-containing wells and can open and close in time, and the purposes of improving the pump efficiency and avoiding airlocks are achieved.