For the small tampered region coming from two times of JPEG compression with inconsistent block segmentation in composite JPEG images,in this paper,an effective shifted double JPEG(SD-JPEG) compression tampering detection method based on conditional co-occurrence probability matrix(CCPM) is proposed.In order to reduce the effects caused by the diversity of image content and enhance the SD-JPEG compression,difference 2-D arrays are generated along four directions,i.e.,horizontal,vertical,main diagonal and minor diagonal directions,for magnitudes of JPEG quantized discrete cosine transform(DCT) coefficients.The thresholding technique is used to deal with these difference arrays for reducing computational cost.Conditional co-occurrence probability matrix is used to model these thresholded difference 2-D arrays.All elements of these conditional co-occurrence probability matrices are served as features for SD-JPEG compression tampering detection.Principal component analysis(PCA) is introduced to reduce the dimensionality of the proposed features.Support vector machine(SVM) is employed as the classifier to identify whether an image block has been SD-JPEG compressed.Experimental results demonstrate the effectiveness of the proposed method.