Disclosed is an RFID tag antenna with an isolation groove, comprising a first antenna and a second antenna with an adjustable distance therebetween. The RFID tag antenna has a long reading distance that can reach 11 m to 13 m according to tests, and is extendable, that is, has an adjustable length. The RFID tag antenna is applicable to a suite with a substantially fixed width and an undetermined length, features good antenna performance, small standing-wave ratio, low return loss, high gain, and omnidirectivity, and therefore has great practical value.