To explore the effect of crude ammonium perchlorate (AP) crystal′s surface defects on the combustion and mechanical properties of HTPB propellant, the crystal morphologys of two kinds of crude AP (40-60 mesh (Ⅰ), 100-140 mesh (Ⅲ)) were observed by scanning electron microscope(SEM), and the effects of crude AP′s morphology defects on burning rate, pressure exponent and mechanical properties of HTPB propellant were studied. The results show that there is little effect of crude AP′s morphology defects on the burning rate and pressure exponent of HTPB propellant′s low-pressure section (3-12 MPa), whereas a noticeable effect on those of its high-pressure section (12-20 MPa). The burning rate of high-pressure section expands the scope from 11.27-13.93 mm·s^-1 to 11.28-16.35 mm·s^-1 and the pressure exponent also increases from 0.40 to 0.70 when the morphology defects appear on the surface of crude AP crystals. The results also show that crude AP′s morphology defects have little effect on the mechanical properties of HTPB propellant.