The invention discloses a method of detecting radiosensitivity of lung cancer cells on x ray, a chip and an application. The method comprises the following steps: selecting lung cancer cells which are abnormally sensitive to and tolerant to radiotherapy; detecting expression difference of micro RNA in two groups of cells by using a micro RNA expression profile chip; verifying the chip result by means of a Real-Time PCR technology; and finally, screening 11 microRNAs which has remarkable difference. The method disclosed by the invention can be used for predicting sensitivity of the lung cancer cells on radiotherapy.