The invention relates to a high water pressure split type rock mass deformation measuring device and a construction method and application of the device. The device adopts the LVDT sensor principle tocarry out a split type and high water pressure prevention design, and main components of the device comprise a metal measuring bar, a magnetic iron core, a shell, a waterproof coil framework, a coil,a tail attachment, a wire clamp, a cable, a signal processing bin and the like; the main electronic components are treated by adopting a full-metal shell and vacuum particle sealing double-layer sealing process and has the water pressure resistance of 5 MPa or more; And measured signals have the characteristics of centralized processing, digitization and signal dual utilization, namely, after data of a plurality of sensors are centralized and processed by one electronic bin, the digitized signals are connected with an independent reading instrument outside the bin or a centralized acquisitiondevice of a field experiment. The high water pressure split type rock mass deformation measuring device realizes the upgrading from the traditional manual recording to the digital data transmission,real-time viewing and acquisition, and has the advantages of high water pressure resistance, interference resistance, high precision, suitability for the overall test requirement, quick dynamic response, long service life and the like.