Beam sampling by a fused-silica grating, which sampling the full-aperture beam, is focused on a diagnostics sensor to measure the laser pulse shape of technical integration lines of Shenguang-Ⅲ. The optical path of sampling beam at focus spots is not equal, so the pulse shape is different from the original pulse. Research on laser temporal profile measurement by means of grating are reported. The model to reconstruct the pulse shape is developed to study the superposition of sampling pulse, and spatial uniformity and optical path are considered. Simulation indicated that sampling has only a small impact on the pulse shape of beam, which aperture is 290 mm×290 mm, pulse duration is more than 1 ns, focus length of sampling beam is 1380 mm, and the angle is 11.5°. The calibration results show that the diagnostic technology of sample with grating is feasible for laser measurement. The technology is a great success in the laser temporal diagnostic of technical integration lines of Shenguang-Ⅲ.