The utility model discloses a level adjustment device, including bottom sprag mechanism, support group spare and adjustment platform, bottom sprag mechanism is used for supporting fuel assembly, the mechanism in bottom sprag is connected to the one end of support group spare, and it is used for supporting measuring device, the adjustment platform is including following the guiding mechanism that the first direction moved and can following the 2nd guiding mechanism that the second orientation moved, and the 2nd guiding mechanism connects between a guiding mechanism, support group spare, and thefirst direction is crisscross mutually with the second orientation, and a guiding mechanism, the 2nd guiding mechanism move and adjust by support group spare drive bottom sprag mechanism. Consequently, can realize that the adjusting range is great to measuring device's long -range level adjustment on fuel pond limit, adjustment accuracy is higher, can satisfy the measurement accuracy requirement,and level adjustment device's simple structure, easy manual operation, and operational safety is good.