The invention relates to an intelligent wristband with an automatic tightening function. The intelligent wristband comprises a body and a fastening mechanism arranged at two sides of the body, wherein the fastening mechanism comprises a watchband, a watchband sleeve and a fastening assembly, a fastening groove is arranged inside the watchband sleeve, the watchband is matched with the fastening groove, and the watchband is in transmission connection with the watchband sleeve through the fastening assembly. For the intelligent wristband with the automatic tightening function, the watchband is embedded in the fastening groove inside the watchband sleeve, a magnet is matched with an embedding sleeve, an electromagnetic wire in the embedding sleeve adsorbs the magnet, then a stretching motor hauls in the watchband through a push-pull rod, so that the tightness degree of the watchband and the watchband sleeve is controlled, and the practicability of the intelligent wristband is improved; moreover, in a working power supply circuit, an integrated circuit charges a first capacitor, then the given voltage value is achieved, the output voltage value of a second capacitor is twice of the given voltage value, thus the instantaneous high output voltage is guaranteed, and finally, the practicability of the intelligent wristband is improved.