A new method of reducing the laser thermal effect on the properties of giant magnetoresistance-spin valve (GMR-SV) using optical thin films was investigated. A GMR-SV device, a biosensor with a size of 2 x 2 mu m(2) and an MR of 2.3%, was fabricated. [TiO(2)/SiO(2)](14)/TiO(2)/Air was deposited on a glass/[GMR.-SV] multilayer as an alternate optical thin film (OTF) by using a rf magnetron sputtering system. The surface resistance of the GMR, with the OTF coating under a He-Ne laser was 1% less than that of the GMR with a photoresist (PR) coating. A GMR-SV with metal multilayer can be protected from the laser thermal effect by using OTF.