An RFID electronic seal includes a head and a strap. A through-hole extends from a first side through a second side of the head. The strap includes an end extending from the first side of the head. A tag is embedded in the head or the strap. A signal-transmitting line is embedded in at least one of the head and the strap and extends from the tag. The strap is extendable through the through-hole of the head along a tightening direction, forming a tightening space, with an engaging member on the strap engaging with another engaging member on the head to prevent the strap from moving in an unfastening direction. The electronic seal can be used in a tracking system that allows a cargo or goods owner to notice breakage of the electronic seal in real time.