With　the　rapid　development　of　communication　technology,　there　is　a　widespread　use　of　mobile　telephone,　whose　effect　on　human　has　been　getting　more　and　more　attention.　The　electromagnetic　wave　can　penetrate　biosystems　and　interacts　with　biological　tissue　at　different　biological　levels.　Although　many　researchers　have　been　studying　biological　effects　of　electromagnetic　radiation　for　years,　their　results　are　not　consistent　and　need　to　be　confirmed　by　reliable　and　repeatable　experiments.　Since　the　energy　of　electromagnetic　radiation　of　mobile　phone　is　much　low　and　the　organism　has　an　adaptability　to　external　stimulation,　short　-time　radiation　may　not　induce　obvious　effect　on　organism.　To　avoid　other　inductive　factors　in　the　environment,　we　used　in　vitro　cell　culture　technology　and　exposure　experiment　to　study　the　activating　effect　of　900　MHz　electromagnetic　fields　(EMF)　on　NIH/3T3　cells.　NIH/3T3　cells　are　sensitive　to　sarcoma　virus　focus　formation　and　leukaemia　virus　propagation,　and　therefore　are　often　used　for　DNA　transformation　studies.　The　NIH/3T3　cells　were　divided　into　four　groups,　the　control　group　with　sham　exposure　and　the　three　exposure　groups　exposed　to　10W/m2,　50W/m2　and　90W/m2　916MHz　EMF　respectively.　The　exposure　lasted　2　hours　a　day.　After　exposure　we　found　the　cells　morphology　changed　and　had　the　characteristics　of　epithelial　cells.　The　Soft　agar　assay　showed　that　all　the　exposure　groups　formed　colonies　in　soft　agar　while　the　control　group　did　not　form　colonies.　The　results　in　this　study　suggest　that　916MHz　electromagnetic　waves　can　promote　malignant　transformation　of　NIH/3T3　cells　and　induce　cellular　canceration.