Stride across karez high -speed railway subgrade strengthening structure to effective technological problem who stridees across the design of karez high -speed railway and face that solves satisfies high -speed railway road bed safety and stability and warp the control requirement, and remains the existing retaining of karez, drainage function. It including the karez reinforced structure that is located road bed influence scope, set up adding the muscle bed course and building at the embankment with on the muscle bed course on the karez reinforced structure, the karez reinforced structure includes that the dendroid blocks masonry dam, underdrain obsturator, loaded filter and shaft obsturator, and the dendroid is blocked the masonry dam and is builded the lower extreme at karez underdrain, and the underdrain obsturator fills in karez underdrain, and the loaded filter setting is in karez underdrain upper end, and the shaft obsturator fills in the karez shaft.