A novel method for the determination of trace cobalt by thermal lens spectrometry after cloud point extraction(CPE) has been developed.It is based on CPE of cobalt(Ⅱ) ions as 2-(3,5-dichloro-2-pyridylazo)-5-dimethylaminoaniline(3,5-diCl-PADMA) complexes usingoctylphenoxypolyehtoxyethanol(TritonX-114)as a nonionic surfactant.