Abstract: The Dragon-Ⅰlinear induction accelerator(LIA) uses mm level diameter pulsed electron beam to strike the bremsstrahlung converter target to generate X-ray, which generates the backstreaming ions as well. Four Faraday cups are combined to collect backstreaming ions produced at the bremsstrahlung converter target of the Dragon-ⅠLIA. Experiment and calculation results show that the backstreaming positive ions density and velocity are about 1021/m3 and 2～3 km/s,respectively.The calculated results show that the intensity of the backstreaming positive ion beam is only 0.27% of that of the targeting electron beam, thus the backstreaming ions would not affect the focus of the electron beam.