The invention discloses a pre-diluted vacuum blood collection tube, which comprises a tube body and a tube plug, wherein a tube cap is arranged at the outer side of the tube plug; the tube body, which is sealed, is under a vacuum state; scale marks, which are used for marking capacity of the tube body, are arranged on the outer wall of the tube body; scale values, indicated by the scale marks, range from 9mL to 10.5mL, and a minimum division value is 0.1mL; and 9mL of sodium chloride injection or compound electrolyte injection is contained in the tube body. The invention also discloses a method for measuring platelet number in a patient with EDTA-dependent pseudo-thrombocytopenia with the application of the pre-diluted vacuum blood collection tube. The pre-diluted vacuum blood collection tube provided by the invention is simple in structure; the pre-diluted vacuum blood collection tube is designed with the precise scale marks; venous blood is diluted by liquid which is free from an anticoagulation, so that autologous antigen in an anticoagulation-induced and activated platelet membrane glycoprotein GPIIb structure, and a purpose of inhibiting platelet aggregation is achieved; and the pre-diluted vacuum blood collection tube, through a mode of vacuum blood collection, simplifies operations and avoids pollution, caused by open blood collection, to operators and environment.