The invention provides a naked flame spreading prevention isolated extinguishing safety power supply for a computer room. The safety power supply comprises a power supply mounting rack. A power supply main body is mounted on the power supply mounting rack. An annular box is arranged on the periphery of the top of the power supply mounting rack. The periphery of the annular box is provided with an annular groove. The annular groove is filled with a flameproof fabric. One end of the flameproof fabric is connected with the inner wall of the annular box. The other end of the flameproof fabric is connected with a plurality of plug rods. The top of the power supply mounting rack is provided with supporting rods. A top cover is mounted on the tops of the supporting rods. A plurality of sleeve pipes are mounted on the periphery of the top cover. One end of each sleeve pipe is provided with an opening and is arranged downwards slantly. By adopting the safety power supply, when a fire occurs to the power supply, a layer of fireproof enclosure can be formed rapidly to confine part of flames within a region formed by the flameproof fabric. The fireproof enclosure can reduce inflowing air to make burning incomplete and even make the flames be extinguished through oxygen deficit. Meanwhile, the flames are prevented from spreading around, and the influence of the fire is reduced. The safety power supply can be effectively applied to large power supply equipment and can reduce the influence of fires on other devices and damage of fires to other devices.