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The stability of tunneling in the underground mine is an important factor in the production of mines that must ensure productivity and safety. In Antam Underground Gold Mine, the production cycle starts by drilling the tunnel then charge the explosive material. After that, the tunnel is blasted before the ore mucking activity. The activity continues to reinforcing the tunnel and back again to the beginning of the cycle, drilling activity. The drilling is using Jumbo Drill which has 3-meter drilling rod. With span progress is about 2.7 from 3 meters or 90% of the drilling rod length, in a tunnel with dimension 5-meter-high and 5-meter-wide, the mining is producing 170 tons in 8 hours which can be considered the productivity 21.25 ton per hour each Jumbo Drill. Among many rock conditions affecting stability, the width and height of tunnel are an important design factor. In this paper, the aim is to optimizing blasting activity by considering the maximum unsupported span (MUS) using the Q system. The mining factor like the equipment size, geological condition and productivity cycle are combined and considered to get the optimum span value in a variety of rock mass at Antam Underground Gold Mine. The output of the research is the maximum unsupported span value has a variety figure from 1.8 to 8 meters depending on the rock mass characteristic. By observing the mining operation factor, the maximum span can be proposed in 4.2-meter length. Although the drilling time getting longer 20%, the production tonnage increase 40% which mean productivity also climb 20%. As a result, by utilize MUS and considering the mining factor, the productivity can be enhanced and safety guaranteed.