The invention discloses a liquid injection cup unit, comprising a cup body, an in-cup rod, a pipeline and a connecting block, the cup body is provided with a liquid injection chamber and a liquid injection channel communicated with the liquid injection chamber; an inner pipe is arranged in the liquid injection chamber; the lower end of the inner pipe is close to the inner bottom of the liquid injection chamber, and the upper end of the inner pipe is communicated with the connecting block; one end of the connecting block is communicated with pipeline, and the other end of the pipeline is communicated with a liquid injection nozzle; the in-cup rod is internally provided with a channel, and the lower end of the in-cup rod is provided with a plugging head; the in-cup rod is slidably arranged; when the in-cup rod slides to a first position, the plugging head plugs the upper end of the inner pipe so as to allow the outlet of the channel to be communicated with the pipeline via the connecting block; and when the in-cup rod slides to a second position, the plugging head leaves the upper end of the inner pipe so as to allow the inner pipe to be communicated with the pipeline via the connecting block. The liquid injection cup unit provided by the invention completes vacuum pumping and liquid injection at a same station, so liquid injection efficiency is effectively improved, liquid injection is thorough, and residual liquid is prevented from leaking from a liquid injection opening.