The present study aims to achieve the highest cumulative yield of the hemispherical distillers, by designing and constructing new reflector mirrors, which are truncated circular cone-shaped reflector mirrors (TCC-RM). To obtain the optimum inclination of TCC-RM that achieves a highest hemispherical distiller's performance, eight inclination angles ( 10o , 15 o , 20 o , 25 o , 30 o , 35 o , 40 o and 45 o with vertical) was experimentally studied. To achieve this, a series of experimental tests were carried out on the three hemispherical solar distillers, the first represents the reference distiller (traditional hemispherical solar distiller-THSD) and the other two devices are the hemispherical solar distiller with truncated circular cone-shaped reflector mirrors (HSD-TCCRM) with different inclination angles. The experimental results indicate that utilizing TCC-RM with a 25 o inclination angle achieves the maximum cumulative yield of 8.35 L/m 2 with an improvement of 42.74% compared to THSD. While the utilization of TCC-RM with the inclination angles by 30 o , 35 o , 20 o , 40 o , and 15 o achieves the cumulative yield of 7.