Objective To investigate the influence of intensity-modulated radiation pattern on ra-diobiological effects of nasopharyngeal carcinoma cell line CNE2.Methods Colony formation assay was used to calculate cell surviving fraction, and compare the cell survival curves and the surviving fraction with single-hit multi-target model fitting survival curves to different delivery time and dose rates.Results ⑴Nasopharyngeal carcinoma cell line CNE2 was irradiated on two models:conventional radiation ( CR) mod-el;intensity modulated radiation model ( IMRT model, which was divided into 10 min IMRT irradiated group, 15 min irradiated group, and 20 min irradiated group) .Except that the parameters of radiation biol-ogy did no significantly differ between CR model and 10 min IMRT irradiated group ( P >0.05) , the other groups among radiobiology parameters surviving fraction (SF2), quasi-threshold dose(Dq) and extrapolation number(N) were all significant differences ( P <0.05) .⑵ They found that the SF2 300 Mu/min>SF2 600 Mu/min ( P <0.05) when the CNE2 cells were treated with dose rates of 300 Mu /min and 600 Mu/min.Conclusions ⑴There were not significant changes in the biological effects until the delivery time prolonged to more than 10 minutes.When the delivery time extended to more than 15 minutes, the survival fraction was increasing with the radiation time risen.⑵The dose rates used in the experiment did not show any effect on the radiobiology parameters without SF2 .