Ion-current density is a significant indicator of electromagnetic environment under HVDC（high voltage direct current） lines. To improve measurement accuracy and convenience

we concluded factors that affect measurement results and proposed a wireless measurement method. The Wilson plate was designed according to the IEEE standard

a nano-ammeter was employed to condition the ion-current signal

and after being digitalized by the wireless terminal

the signal was transmitted to the upper computer via Zig Bee

moreover

an automatic measurement software was developed. Finally

the measurement system was calibrated and some field tests were performed. The results show that the measurement system possesses the merits of good accuracy

simple structure

convenient operation

high stability

and reliability

the maximum current measurement error is about 5%

and typical measurement error is less than 3%. The wireless transmission improves probability and reduces preparation time dramatically. This method can be used in field measurement and lateral distribution of ion-current density.