The invention relates to the field of medical apparatuses, in particular to an air pressure automatic simulation apparatus for detecting a negative pressure capacity of a vacuum blood-collecting tube. The apparatus comprises an air pressure simulation box and an simulation sampling device arranged in the air pressure simulation box; the air pressure simulation box is of a box structure with a box door at the front side; two air nozzles are densely embedded in the middle of a back plate of the air pressure simulation box and connected with an air pipe; an electronic pressure sensor is arranged on the upper inner wall of the air pressure simulation box; the electronic pressure sensor is electrically connected with a main control panel. According to the air pressure automatic simulation apparatus for detecting the negative pressure capacity of the vacuum blood-collecting tube, production enterprises or government quality supervision organizations can easily simulate the specified air pressure environment of the vacuum blood-collecting tube and the actual blood-collecting capacity in the air pressure environment is presented, in order to detect whether or not the vacuum blood-collecting tube is suitable for nominal air pressure environment. By means of the apparatus, the nominal capacity detection of the vacuum blood-collecting tube under the nominal air pressure is simple, convenient and quick, and more accurate.