A foam spray head assembly 100 comprising: a push head 1 connected with a mounting member 2; a netted member 3 having a first net 32 and a second net 33; an air valve 4 having a first groove 41 and a second groove 42, the air valve 4 having a first end thereof connected to the first net 32 and mounted to the push head 1, a second end of the air valve 4 connected with the second net 33; a main plunger 5 being a hollow tube and having a first plunger 51, a second plunger 52, a flange portion 53 and a lip 54, the first plunger 51 being located in the second groove 42 and defining a first chamber 40, a first gap 50 being defined between an outer surface of the first plunger 51 and an inner surface of the second groove 42; a piston unit 6 having a hollow first piston 61 and a second piston 62, the first piston 61 having a third groove 611, a fourth groove 612 and a seal ring 613, an intake slot 411 defined between a top end 6121 of the fourth groove 612 and an inner surface of the first groove 41, a second gap 60 defined between a bottom end 6122 of the fourth groove 612 and the flange portion 53, the seal ring 613 movably contacting the lip 54 of the main plunge 5, the second piston 62 having a fifth groove 621 and a sixth groove 622, the second piston 62 connected to the second plunger 52; a rod unit 7 extending through the main plunger 5 and having a rod 72 extending through the second piston 62, the rod 72 and the sixth groove 622 being located in the second plunger 52, a third gap 70 defined between the rod unit 7 and an inner surface of the second plunger 52; a resilient member 8 mounted to the second plunger 52 and having an end contacting the flange portion 53; a cylinder unit 9 connected to the mounting member 2 and having a first cylinder 91 and a second cylinder 92, the first piston 61 being movable in the first cylinder 91 and forming an enclosed second chamber 80, the second piston 62 being movable in the second cylinder 92 and forming an enclosed third chamber 90, and a valve 10 being in contact with an opening 921 of the second cylinder 92, characterized in that the rod unit 7 includes another rod 71, the two rods 72 & 71 being connected by a connection portion 73, the other rod 71 having an annular flange 711 on a first end thereof which is movably in contact with an inner surface of the first plunger 51 and generates a fourth gap 7110 when opened to allow the liquid in the third chamber 90 to flow into the first chamber 40 through the fourth gap 7110 so that the liquid and the gas are mixed, and that a ring 93 is located between the first and second cylinders 91, 92. a push head 1 connected with a mounting member 2; a netted member 3 having a first net 32 and a second net 33; an air valve 4 having a first groove 41 and a second groove 42, the air valve 4 having a first end thereof connected to the first net 32 and mounted to the push head 1, a second end of the air valve 4 connected with the second net 33; a main plunger 5 being a hollow tube and having a first plunger 51, a second plunger 52, a flange portion 53 and a lip 54, the first plunger 51 being located in the second groove 42 and defining a first chamber 40, a first gap 50 being defined between an outer surface of the first plunger 51 and an inner surface of the second groove 42; a piston unit 6 having a hollow first piston 61 and a second piston 62, the first piston 61 having a third groove 611, a fourth groove 612 and a seal ring 613, an intake slot 411 defined between a top end 6121 of the fourth groove 612 and an inner surface of the first groove 41, a second gap 60 defined between a bottom end 6122 of the fourth groove 612 and the flange portion 53, the seal ring 613 movably contacting the lip 54 of the main plunge 5, the second piston 62 having a fifth groove 621 and a sixth groove 622, the second piston 62 connected to the second plunger 52; a rod unit 7 extending through the main plunger 5 and having a rod 72 extending through the second piston 62, the rod 72 and the sixth groove 622 being located in the second plunger 52, a third gap 70 defined between the rod unit 7 and an inner surface of the second plunger 52; a resilient member 8 mounted to the second plunger 52 and having an end contacting the flange portion 53; a cylinder unit 9 connected to the mounting member 2 and having a first cylinder 91 and a second cylinder 92, the first piston 61 being movable in the first cylinder 91 and forming an enclosed second chamber 80, the second piston 62 being movable in the second cylinder 92 and forming an enclosed third chamber 90, and a valve 10 being in contact with an opening 921 of the second cylinder 92, characterized in that the rod unit 7 includes another rod 71, the two rods 72 & 71 being connected by a connection portion 73, the other rod 71 having an annular flange 711 on a first end thereof which is movably in contact with an inner surface of the first plunger 51 and generates a fourth gap 7110 when opened to allow the liquid in the third chamber 90 to flow into the first chamber 40 through the fourth gap 7110 so that the liquid and the gas are mixed, and that a ring 93 is located between the first and second cylinders 91, 92.