A washing machine and a detergent delivery pump assembly thereof are provided. The detergent delivery pump assembly includes a pump defining a plurality of fixed-volume chambers therein for containing detergents respectively, each fixed-volume chamber being provided with a liquid inlet valve and a liquid outlet valve; a plurality of pistons disposed in the plurality of fixed-volume chambers in one-to-one correspondence relationship and each including piston head, the piston head being controlled to reciprocate in the fixed-volume chamber to draw or push out a fixed volume of detergent; a motor assembly; and a transmission mechanism to associate the piston heads with the motor assembly, such that the piston heads are controlled to move in the fixed-volume chambers by the motor assembly.