The invention discloses an injection moulding method of a polydimethylsiloxane microfluidics chip. A polydimethylsiloxane former polymer and a curing agent are evenly mixed, the evenly-mixed polydimethylsiloxane former polymer and curing agent mixture is subject to vacuumizing treatment in a seal device until bubbles in the mixture completely disappear; a mould on an injection moulding machine is preheated, vacuumizing is carried out, the polydimethylsiloxane former polymer and curing agent mixture with the bubbles removed is injected into the mould on the injection moulding machine, and injection moulding is carried out on the mould of the injection moulding machine; after injection moulding is completed, organic solvents of chloroform, dichloromethane or methylbenzene and the like are used for cleaning the mould, obtained after injection moulding, of the injection moulding machine; the whole preparing process is simple, shorter in period, free of complex equipment, low in cost and high in moulding precision; particularly, large-scale and batch production of the polydimethylsiloxane microfluidics chip can be achieved.