The utility model relates to a reducing connecting device's borehole television probe is equipped with belongs to the engineering check out test set field of making. It comprises borehole television probe, reducing connecting device and transparent safety cover, and reducing connecting device sets up between borehole television probe and transparent safety cover, is equipped with connecting thread on reducing connecting device's internal face and the outer wall respectively, and the lower extreme rotary seal of reducing connecting device upper end and borehole television probe connects, and the upper end rotary seal of reducing connecting device lower extreme and transparent safety cover connects. The utility model discloses a set up a reducing connecting device in borehole television probe lower part and transparent safety cover upper portion. Use the borehole television probe of a minor diameter, through reducing connecting device, change the transparent safety cover of different diameters, reach the mesh of the various different diameters of test drilling to it pops one's head in with a borehole television to realize tests the drilling of multiple diameter, reduces the quantity of carrying of borehole television probe, improves the utilization ratio of borehole television probe.