Industrial computed tomography (ICT) adopts generation III scan mode to execute the rapid test of objects. However, generation III has the small filed of view limited by the length of the detector. It is difficult to test the large objects rapidly. In order to realize the rapid ICT test of large objects, a scan mode called half-scan was discussed and its filter back-projection (FBP) reconstruction algorithm was deduced. This algorithm firstly modified the fan-beam projection data acquired by half-scan into the in-completed parallel-beam data at 0°~360° with the rebin reconstruction principle of fan-beam generation III CT. Then the completed parallel-beam data at 0°~180°was created with the symmetry of parallel-beam. Finally CT reconstruction was executed with parallel-beam reconstruction algorithm. The validity of half-scan mode was verified by the results of computer simulation and experiments. Analysis shows that the effective scan field of view can be improved more than 80% compared with that of generation III.