A portable pump by which liquid may be horizontally pressed out, comprising a liquid storage container, and a pump head provided on a side of the liquid storage container; a liquid suction device connected to the pump head is provided in the liquid storage container, the liquid suction device comprises a liquid suction chamber, a spring, a piston, and a liquid outlet pipe connected to the pump head, the liquid suction chamber is provided with a liquid inlet pipe and a fixed end of the spring, the liquid outlet pipe and the liquid inlet pipe are provided with a check valve (71,72), respectively; the piston is sleeved with the liquid outlet pipe and is provided with a through hole matching with an opening of the liquid outlet pipe; one end of the spring is fixed at the fixed end, and the other end thereof is connected to the piston, and under the pressing of the pump head, the piston is driven to move horizontally in the liquid suction chamber; when the piston is reset, the stored liquid in the liquid storage container is pumped into the liquid suction chamber from the liquid inlet pipe; when the piston is pressed, the stored liquid in the liquid suction chamber is squeezed into the liquid outlet pipe and pumped out of the pump head; characterised in that the pump further comprises a locking structure of the pump head, wherein the pump head is shaped as a cap, the locking structure is a locking seat provided on the side of the liquid storage container and matching with a pump head cover, the locking seat has a ring opening provided in a form of an annular opening, a positioning block is provided in the ring opening; a convex ring sleeved with the ring opening is provided at a bottom of the pump head, and the convex ring is provided with a notch and a limiting convex edge; when the pump head is operated to rotate, the convex ring rotates axially in the ring opening, and when the notch is aligned and embeddedly matched with the positioning block, the pressing movement of the pump head is unlocked; otherwise the positioning block and the convex ring are abutted with each other, thereby limiting the pressing operation of the pump head, wherein a depth of the notch is adapted to a height of the positioning block and matches with a horizontal displacement stroke of the piston in the liquid suction chamber; and the convex ring is further provided with a positioning groove, one end of the limiting convex edge is connected to the notch, and the other end thereof is connected to the positioning groove; the positioning block rotates along with the pump head, slides against and along the surface of the convex ring until the positioning block reaches the limiting convex edge and is embedded in the positioning groove, such that the pump head is in a locked state. the pump further comprises a locking structure of the pump head, wherein the pump head is shaped as a cap, the locking structure is a locking seat provided on the side of the liquid storage container and matching with a pump head cover, the locking seat has a ring opening provided in a form of an annular opening, a positioning block is provided in the ring opening; a convex ring sleeved with the ring opening is provided at a bottom of the pump head, and the convex ring is provided with a notch and a limiting convex edge; when the pump head is operated to rotate, the convex ring rotates axially in the ring opening, and when the notch is aligned and embeddedly matched with the positioning block, the pressing movement of the pump head is unlocked; otherwise the positioning block and the convex ring are abutted with each other, thereby limiting the pressing operation of the pump head, wherein a depth of the notch is adapted to a height of the positioning block and matches with a horizontal displacement stroke of the piston in the liquid suction chamber; and the convex ring is further provided with a positioning groove, one end of the limiting convex edge is connected to the notch, and the other end thereof is connected to the positioning groove; the positioning block rotates along with the pump head, slides against and along the surface of the convex ring until the positioning block reaches the limiting convex edge and is embedded in the positioning groove, such that the pump head is in a locked state.