A detergent box assembly for a washing machine, comprising: a detergent box provided with an upper cover subassembly; a distributor box having a front plate, a rear plate and a receiving chamber provided therebetween, said receiving chamber configured to store a laundry treat agent, the distributor box being movably disposed within the detergent box and adapted to move between an open position and a closed position, a key-press being provided in the front plate; a lock catch associated with the key-press and provided at the distributor box; and a driving subassembly configured to drive the distributor box to move from the closed position to the open position when the key-press is pressed; characterized in that the driving subassembly comprises: a gear assembly; a rack; and a tension spring; wherein the gear assembly is disposed on the upper cover subassembly of the detergent box; the rack is provided on the upper cover subassembly of the detergent box and adapted to be engaged with the gear assembly, the rack having a free end adjacent to the front plate of the distributor box and a snap-fit end away from the front plate of the distributor box and opposite to the free end along a length direction thereof, the snap-fit end of the rack being configured to be engageable with the rear plate of the distributor box and formed with a downwardly-extending leg engageable with the rear plate of the distributor box; and the tension spring is disposed along the length direction of the rack and has a first end and a second end opposite to the first end, the first end being adjacent to the front plate of the distributor box and mounted on the upper cover subassembly of the detergent box, the second end being coupled to the rack and adjacent to the snap-fit end of the rack; wherein the lock catch is configured to be lockably engaged by the washing machine such that when the key-press is pressed, the lock catch is unlocked and disengaged by the washing machine, the rack is driven by the tension spring to enable the distributor box to be moved from the closed position to the open position, and the upper cover subassembly of the detergent box comprises a first cover part and a second cover part assembled with each other, the second cover part is provided with a mounting slot and the rack is mounted within the mounting slot of the second cover part. a detergent box provided with an upper cover subassembly; a distributor box having a front plate, a rear plate and a receiving chamber provided therebetween, said receiving chamber configured to store a laundry treat agent, the distributor box being movably disposed within the detergent box and adapted to move between an open position and a closed position, a key-press being provided in the front plate; a lock catch associated with the key-press and provided at the distributor box; and a driving subassembly configured to drive the distributor box to move from the closed position to the open position when the key-press is pressed; characterized in that the driving subassembly comprises: a gear assembly; a rack; and a tension spring; wherein the gear assembly is disposed on the upper cover subassembly of the detergent box; a gear assembly; a rack; and a tension spring; wherein the gear assembly is disposed on the upper cover subassembly of the detergent box; the rack is provided on the upper cover subassembly of the detergent box and adapted to be engaged with the gear assembly, the rack having a free end adjacent to the front plate of the distributor box and a snap-fit end away from the front plate of the distributor box and opposite to the free end along a length direction thereof, the snap-fit end of the rack being configured to be engageable with the rear plate of the distributor box and formed with a downwardly-extending leg engageable with the rear plate of the distributor box; and the tension spring is disposed along the length direction of the rack and has a first end and a second end opposite to the first end, the first end being adjacent to the front plate of the distributor box and mounted on the upper cover subassembly of the detergent box, the second end being coupled to the rack and adjacent to the snap-fit end of the rack; wherein the lock catch is configured to be lockably engaged by the washing machine such that when the key-press is pressed, the lock catch is unlocked and disengaged by the washing machine, the rack is driven by the tension spring to enable the distributor box to be moved from the closed position to the open position, and the upper cover subassembly of the detergent box comprises a first cover part and a second cover part assembled with each other, the second cover part is provided with a mounting slot and the rack is mounted within the mounting slot of the second cover part.