The temperature and external AC magnetic field dependence of AC magnetization losses of MgB 2 wires were studied. Temperature was varied from 18K to 40K and external magnetic field of frequencies 72Hz and 144Hz from 8mT to 70mT with orientation perpendicular to the wire axis. To clarify the influence of the wire construction on AC loss, single and six filament untwisted samples of length ∼50mm were examined. For this purpose unique experimental apparatus created by the combination of original calibration-free measuring system designed for ac magnetization loss measurement and non-magnetic vacuum vessel with two-stage cryocooler for sample cooling was used. It was found, that for monofilament sample hysteretic AC losses was dominated in comparison to untwisted six-filaments sample, where coupling losses confirmed by frequency dependence were dominated.