The invention discloses a handheld portable precision strain gauge, which belongs to the field of strain measurement of materials. The handheld portable precision strain gauge is characterized in thatinput voltage is subjected to digital sampling through an input end AD converter 1 and becomes digital signals, and the digital signals are isolated through an isolation device 2 and are then inputted to a single chip microcomputer 4 for over-voltage/under-voltage comparison; output voltage is subjected to digital sampling through an output end AD converter 3 and becomes digital signals, and thedigital signals are directly inputted to the single chip microcomputer 4 for over-voltage/under-voltage comparison; the data of the temperature of a working environment are obtained by a temperature sensor 6 and are inputted to the single chip microcomputer 4 for temperature comparison; the single chip microcomputer 4 displays a final comparison result through a display part 5; the single chip microcomputer 4 generates a command of whether to turn off according to the comparison result and carries out unified on and off control on a DC/DC isolation power module through the isolation device 2;and an external control command is inputted to the single chip microcomputer 4 through a control interface 7 to further manually control a power supply group.