Abstract: A CMOS image sensor for direct X-ray imaging without scintillator was designed. The charge collecting mechanism was theoretically analyzed, and radiation-hardened structure for its sensitive element was designed. The line array with different sensitive elements in pixel was taped out in 0.5 μm DPTM standard CMOS technology and tested by X-ray. The experiment results show that the dark signal output voltage of the line array is about 1 V, and saturated output voltage is 2.4 V. The collected charge and parasitic capacitor increase with sensitive elements. Three sensitive elements in one pixel can achieve higher effective output.