Cell　membrane　permeability　is　one　of　the　main　indicators　of　cytotoxicity　and　related　to　many　critical　biological　pathways.　Here,　we　determined　the　Cd2+-induced　membrane　permeability　of　human　MCF-7　cells　using　ferrocene　methanol　molecular　probes　based　on　scanning　electrochemical　microscopy　(SECM).　The　cell　height　and　topography　were　examined　with　an　impermeable　Ru(NH3)(6)Cl-3　probe.　The　membrane　permeability　exhibited　no　significant　changes　when　the　Cd2+　incubation　time　was　less　than　2　h　and　its　concentration　was　less　than　40　mu　M.　The　permeability　increased　when　the　Cd2+　concentration　was　greater　than　60　mu　M,　or　when　the　incubation　time　was　longer　than　3　h.　From　the　combined　3-(4,5-di-methylthiazol-2-yl)-2,5-diphenyltetrazolium　bromide　and　cytoskeleton　imaging　experiments,　it　was　found　that　the　changes　occurred　because　the　cells　exhibited　a　defensive　mode　and　their　membranes　contracted　when　treated　with　a　low　concentration　of　Cd2+　for　a　short　time.　However,　the　cell　membranes　were　irreversibly　damaged　when　the　cytoskeleton　structures　were　destroyed,　and　the　cell　activities　decreased　at　high　concentrations　over　long　periods.　Interestingly,　through　the　comparison　with　an　x-scan　study,　it　was　found　that　DPV　technology　shows　a　higher　performance　in　the　detection　of　changes　in　the　membrane　permeability.　Using　a　combination　of　cytoskeleton　fluorescence　imaging　and　cell-viability　tests,　the　effect　of　the　cadmium　metal　on　the　cell　membrane　permeability　can　be　explored　deeper　and　more　comprehensively.　This　study　provides　a　new　idea　for　exploring　the　changes　in　the　cell　membrane　permeability　and　may　be　helpful　for　rapid　evaluation　of　cytotoxicity.