This artical presents the high resolution study of several Q branches of acetylene in region of v5 band by means of a diode laser spectrometer. The Q branch of (2v4+ v5)I-2v4 band next to 725cm-1 has been observed for the first time. The (v4+v5) -v4 and 2v5-v5 Q branches have been investigated. Some effects of perturbation have been observed. The obtained lines have been least-squares fitted and molecular constants have been obtained.