A Portable transformer neutral point direct current measuring instrument having a wireless transmission function comprises a Hall current sensor (1), a far-end monitoring server (7), and a single-chip microcomputer (2), a service mobile phone (3), a power supply module (4) and a lead-acid battery (5) which are disposed in a box body (6), wherein the output of the lead-acid battery, after conversion via the power supply module, provides work power supply; the single-chip microcomputer is connected through an RS485 circuit and acquires data acquired by the Hall current sensor, and performs data interaction with the service mobile phone through RS232 communication; and the service mobile phone transmits the data to the far-end monitoring server in the form of GPRS. The portable transformer neutral point direct current measuring instrument uses the lead-acid battery for energy supply and transmits signals wirelessly, realizes electric isolation of high-voltage place equipment and low-voltage place equipment, blocks off an overvoltage transmission path, helps to improve the stability and safety of the operation of a detection apparatus, and at the same time helps to solve problems that the direct current monitoring apparatus is difficult to install and the replacement due to failure is difficult to conduct.