Clothes treatment agent release device, washing machine and control method therefor

A clothes treatment agent release device includes: a storage cavity in which a clothes treatment agent is stored; a release cavity with a liquid outlet and a liquid inlet communicating with the storage cavity, a one-way turn-on part arranged at the liquid inlet, and a one-way turn-on part being at the liquid outlet; a reciprocating piston in the release cavity; and a driving mechanism to drive the piston mechanism, the liquid inlet turn-on part/the liquid outlet turn-on part respectively and unidirectionally turn on the liquid inlet/the liquid outlet in the reciprocating motion of the piston mechanism. The clothes treatment agent in the storage cavity is sucked into the release cavity from the liquid inlet, and is discharged and released from the liquid outlet.