The invention discloses a post-embedded monitoring device capable of simultaneously measuring the seepage pressure of groundwater at multiple points. The monitoring device mainly comprises a measuring unit and a sealing unit. The measuring unit is composed of a seepage pressure measuring unit outer pipe, a top isolation bracket, a middle bracket, a sealing material, a line pipe, an osmometer body, a permeable stone, and an osmometer data line. The sealing unit is composed of a sealing unit main pipe, a rubber capsule, a grouting pipe, and an exhaust pipe. The measuring unit and the sealing unit can be expanded by connecting heads and connecting bolts to realize simultaneous measurement at multiple points and to measure and monitor the seepage pressure of groundwater in different water-bearing layers or at different positions of the same water-bearing layer. The monitoring device can be embedded into a position needing measuring and monitoring through drilling in the late period to measure and monitor the pressure of groundwater. The monitoring device can meet the requirements for distribution and location measurement of different water-bearing layers. The monitoring device can be used to measure and monitor the seepage pressure in multiple layers or at multiple positions. The monitoring device is simple in installation, and is convenient and reliable.