The　stability　evaluation　of　deep　foundation　pit　slopes　is　crucial,　including　the　solution　of　the　factor　of　safety　and　the　location　of　the　critical　slip　surface.　Prestressed　anchor　cables　and　underground　diaphragm　walls　are　commonly　used　to　reinforce　pit　slopes.　By　means　of　the　dimensional　increase　technique　and　the　global　analysis　approach　of　slope　stability,　a　nonlinear　optimization　problem　is　defined　for　the　stability　analysis　of　pit　slopes.　In　the　optimization　problem,　the　ordinates　of　discrete　points　on　the　slip　surface　and　the　factor　of　safety　are　both　the　decision　variables,　the　objective　function　is　the　factor　of　security,　and　the　constraints　are　the　equilibrium　equations　and　the　convexity　of　the　slip　surface.　Because　the　objective　function　is　linear　and　the　constraint　functions　are　polynomials　of　degree　three　at　most,　the　optimization　problem　is　a　classical　optimization　one　that　conventional　optimization　techniques　can　solve　without　recourse　to　modern　optimization　techniques　such　as　the　AI　technique.　Examples　suggest　that　the　proposed　procedure　is　far　more　efficient　and　stable　than　the　optimization　models　based　on　the　methods　of　slides.　At　last,　applications　are　demonstrated　to　ongoing　deep　foundation　pit　slopes　situated　at　Tong　Zhou　-　Beijing　sub-center.