Abstract: An X-ray streak camera system with high dynamic range and a long slit photocathode of 30 mm length has been developed for plasma diagnosis in ICF experimental research. In order to enlarge dynamic range and ensure time resolution at the same time, a series of measures are adopted. The measures include reducing electron transit time inside the streak image tube greatly, enhancing the anode's voltage to 16.5 kV, abandoning micro-channel plate electron amplifier, and using fibre plate coupling and air-cooling CCD. An experimental evaluation has been carried out by means of Nd:YAG pico-second laser. The results show that the spatial resolution is 15 lp/mm, the time resolution less than 31 ps and dynamic range more than 922 can be achieved.