The utility model provides a scalable portable terminal fixing device, including mounting mechanism, stretching adjustment mechanism and terminal fixed establishment, mounting mechanism includes pull rod, threaded connecting rod and transverse sliding rod, be equipped with the crotch in the upper end of pull rod, be equipped with the ring cover at the lower extreme of pull rod, threaded connecting rod installs the intermediate position department at transverse sliding rod perpendicularly, the ring cover of two pull rods overlaps respectively to be established on transverse sliding rod's both ends, stretching adjustment mechanism includes vertical duct, transversely pipe and two extension springs, the vertical duct is cross cruciate fixation with horizontal pipe, the upper end screw thread of vertical duct closes on threaded connecting rod soon, two extension springs are connected respectively on the both ends of horizontal pipe, terminal fixed establishment includes expansion plate and two L shape cardboards, expansion plate fixed mounting serves at the lower of vertical duct, two L shape cardboards are installed in the upper and lower side reason of expansion plate upward respectively. This fixing device makes portable terminal have fixed position to put, is favorable to reducing maintainer's work fatigue.