A collinear dual pulse laser induced breakdown spectroscopy (DP-LIBS) has been used for trace element analysis in aluminum alloy. The dependence of signal intensity on the inter-pulse delay time has been carefully investigated, which gives an optimized delay time of about 8～9 μs. For the two selected analytical lines Cu I 324.75 nm and Cr I 425.43 nm, more than 10 folds enhancement of line intensities have been obtained compared to that of single-pulse laser induced breakdown spectroscopy(SP-LIBS). Calibration curves for quantitative measurement of Cu and Cr were derived using both SP-LIBS and DP-LIBS techniques. The limit of detection (LOD) of elements Cu and Cr are found to be 21.46 and 4.26 μg/g respectively with DP-LIBS, while the LOD of elements Cu and Cr are 169.5 and 94.5 μg/g with SP-LIBS.