The invention discloses a fluid-solid-heat coupling triaxial test system for dynamic observation by applying medical CT. The system comprises a triaxial test unit, a medical CT unit and a loading unit for mounting a test piece, wherein the medical CT unit comprises a CT scanning host computer and a sickbed system; the sickbed system is composed of a sickbed fixing bracket and a sickbed movable bracket; the loading unit is located in front of the CT scanning host computer; a straight line guide rail pair structure where the triaxial test unit moves horizontally on a straight line is arranged between the loading unit and the triaxial test unit; a track in the straight line guide rail pair structure is composed of a main body section and an extension section; the main body section is used for moving on the straight line of the loading unit and the extension section is mainly used for moving the triaxial test unit from the loading unit on the straight line to the sickbed moving bracket. The system disclosed by the invention has the beneficial effects that the triaxial test unit can be pushed and pulled into the CT scanner without being hoisted by hoisting equipment, and the system is simple and convenient to operate, and good in safety; and a rock test sample is convenient to assemble and disassemble.