The invention discloses a one-line preplasticizing volume pulse injection forming method and equipment. A preplasticizing device and an injection device are arranged coaxially through a buffering storage chamber formed by a melt transition sleeve and an injection piston inner cavity. In the injection device, a melt pushes a non-return ring to form an axial space between an injection piston and the non-return ring, the injection piston performs periodical pulse displacement, and melt volume periodical pulsation is achieved during storage, metering, injection and pressing maintaining. The equipment comprises the preplasticizing device and the injection device which are arranged coaxially in a one-line mode, wherein the injection device comprises an injection oil cylinder, the injection piston, an injection piston transverse beam, the non-return ring, an injection head, a metering charging barrel, a spray nozzle seat and spray nozzles; the melt transition sleeve, the injection piston, the non-return ring, the injection head, the metering charging barrel, the spray nozzle seat and the spray nozzles are arranged coaxially; the injection piston transverse beam is disposed at one end of the injection piston; the injection piston transverse beam is connected with the injection oil cylinder. By means of the one-line preplasticizing volume pulse injection forming method and equipment, melt volume periodical pulsation is achieved during storage, metering, injection and pressing maintaining.