To　investigate　the　application　of　293　cells　to　detect　suspected　carcinogens　and　provide　experimental　evidence　by　using　in　vitro　cell　transformation　assay　and　tumorigenicity　study.The　transformation　systems　of　cells　cultured　in　vitro　have　been　adopted　to　clarify　the　tumor　promotive　activity　of　Microcystin　LR　(MC-LR).　The　malignant　transformation　of　293　cells　induced　by　MC-LR　is　tested　by　several　methods　including　clone　forming　in　soft　agarose,　serum　requirement　assay　and　tumor　forming　in　mice　to　define　the　promotive　activity　of　293　cells.293　cell　acted　like　tumor　cells　after　induced　by　MC-LR:　serum　dependence　decreased,　anchorage　independence　growth　in　soft　agarose　and　formed　cell　clones,　malignant　tumors　appeared　in　SCID　mice.293　cells　were　easy　to　culture　and　sensitive　to　environmental　carcinogens　so　that　can　be　used　in　detection　of　suspicious　carcinogens.