Objective To observe the proliferation ability of NIH/3T3 cells after a long-term exposure to 1800MHz electromagnetic radiation.Methods Cells were exposed to 1800MHz electromagnetic radiation, at SAR of 2W/kg, intermittently exposure mode (5min on /10min off), 5h/d.Then plate clone forming test and soft agar clone forming test of the exposed and sham exposed cells were cultured respectively after 60-day and 138-day exposure.Telomerase expressions of each group were detected by ELISA.Results In plate clone experiments, plate clone forming ratio was significantly lower than that of the sham group (P<0.05) after 60-day exposure, however, there was no significant difference between the exposed cells and the sham after 138-day exposure.In soft agar clone experiments, soft agar clone forming was no significantly different from sham group after 60-day exposure, however, 138-day exposure group formation was significantly higher than that of the sham group (P<0.05).In telomerase experiments, after 60 days of exposure, the expression of telomerase was no significantly different from sham group, whereas 138-day exposure group was significantly higher than sham group (P<0.05).Conclusions 1800MHz electromagnetic radiation could damage the proliferation of NIH/3T3 cells exposed for 60 days, whereas the ability of cell transformation and proliferation increased significantly after more long-term exposure (138days).