The invention discloses a device for examining the size of a cervical opening, which comprises a hose speculum, wherein an annular mounting ring groove is arranged on the outer round surface of a probe of the hose speculum, a rubber tube is sheathed outside the probe, an annular locating boss is arranged on the inner wall of the front end part of the rubber tube, and the locating boss is clamped in the mounting ring groove on the probe. In the invention, the traditional hose speculum and the rubber tube are skillfully combined, the cervical opening size, the amniotic condition and the fetal presentation height of a pregnant woman can be accurately and quantitively examined, the pain feeling and the uncomfortable feeling of the patient are small, the pain of the patient is greatly reduced,and infection is avoided. Meanwhile, the examining device is simple and convenient to use and has strong operability. The device not only can be used by obstetricians receiving professional training,but also can be operated by the pregnant woman or other people who are given simple introduction. The work intensity of the obstetricians is greatly reduced, the tension of the patient can be effectively released, and problems in the field of cervical opening examination are successfully solved. The device is suitable for large-scale popularization and application.