A collision prevention relational function is disclosed for RFID tags, which increases stability during system operations. The RFID tag includes a parallel resonance circuit having a coil, a resonance capacitor, an adjustment capacitor, a switching circuit, a rectification circuit, a smoothing capacitor, a constant-voltage circuit, a voltage detection circuit, an exclusive OR circuit, a timer circuit, a voltage detection circuit, a control circuit, an OR circuit, a latch circuit, an UID storage device, and a data modulator/demodulator. When a predetermined power supply voltage/operating voltage is obtained, an anti-collision algorithm identifies and adjusts RFID tags that experienced collision.