The invention relates to a dam seepage pressure measuring device. The dam seepage pressure measuring device comprises pressure measuring tubes with top end covers, pressure gages connected with the top end covers and osmotic pressure gauges hung in the pressure measuring tubes, wherein first through holes are formed in the top end covers, cables connected with the osmotic pressure gauges pass through the first through holes and extend to the exteriors of the pressure measuring tubes, inner thread blind holes which are respectively opened towards the pressure measuring tubes are formed in the top end covers, bolts are respectively screwed in the inner thread blind holes, the precession depth of a threaded rod portion of each bolt in each inner thread blind hole is less than the maximum designed screwing depth of each inner thread blind hole, a suspending cable is arranged at the bottom of each bolt, and the bottom of each suspending cable is fixed on each osmotic pressure gauge. According to the dam seepage pressure measuring device, the number of the pressure measuring tubes, which need to be sealed, is decreased, the bolts are virtually connected in the inner thread blind holes and matched with gauge points, and therefore adjustment workload is greatly reduced, and adjustment accuracy is improved.