The invention discloses a switch power source, comprising a pulse width modulation control IC, a MOS tube and a radiating structure; the MOS tube and the radiating structure are fixed together by heat conducting adhesive which comprises following components in parts by weight: 1-2 parts of sodium alga acid, 21.5 parts of butyl rubber, 2.3 parts of hydroxypropyl methyl cellulose, 1.7 parts of sodium alkylarysulfonate, 1.2 parts of triethanolamine, 0.8 part of sodium hydrogen sulfate, 1.3 parts of EDTA, 0.7 part of boron nitride and 0.9 part of nano aluminium hydroxide. The heat conducting adhesive used by the invention is excellent in use performance and long term use of the MOS tube can be ensured.