Aiming at the problem of high false alarm rate or high leakage alarm rate caused by poor quality of low-contrast x-ray carry-on luggage images in airport security, an efficient two-stage x-ray image enhancement scheme is proposed in this paper. First, low and high energy images are fused with Discrete Wavelet Transform (DWT) and Independent Component Analysis (ICA) to implement the first stage enhancement. Then, the proposed Adaptive Sine Gray Level Transform (ASGT) is applied to achieve the second-stage enhancement. Experimental results demonstrate that the proposed algorithm can improve image quality effectively and outperforms other enhancement methods discussed in this paper.