To improve the ductile failure mode and seismic performance of concrete hollow block masonry walls, this study proposes techniques for strengthening these walls with high ductile concrete (HDC). Three unreinforced masonry walls (URM) and three confined walls were built, and then both types were strengthened using single-sided and double-sided HDC layers, respectively. Based on the cyclic loading tests, the failure mode, hysteretic behavior, shear strength and deformation capacity were studied to provide a theoretical basis for the design of such structural members. For the URM walls, HDC layer effectively restricted the development of diagonal cracks, improved the ductile failure mode of wall and increased the shear resistance and deformation capacity. For the confined masonry walls, the strengthened specimens had higher bearing capacity and residual strength, and the damage of the internal masonry walls was slighter. Based on relevant theory analysis，the formulas，for the shear capacity of tested specimens，were proposed. The calculated results matched well with the tested results. Therefore, it can be a reference for the calculation of the shear strength of the strengthened concrete block masonry walls.