Seldom studies have paid attention to investigation of solar-assisted heat pump systems with PCM tank for swimming pool utilization. However, optimal design approaches of solar-assisted heat pump system with PCM tank are still lacking. Thus, this study proposes an optimal design method of solar-assisted heat pump system with PCM tank for swimming pool utilization. TRNSYS and MATLAB are applied to establish simulation platform of investigated system. Influence of solar collector area, air-source heat pump heating capacity, and PCM tank volume on total electricity use, operating cost, thermal uncomfortable ratio, and CO2 emission are analyzed. Total electricity use, operating cost, and thermal uncomfortable ratio are respectively reduced by 8.9 %, 6.8 %, and 33.3 % when solar collector area varies from 2000 m2 to 4000 m2. Central composite design approach is utilized to develop surrogated models. Optimal design in different cases for identifying optimal combinations of key parameters of main components is conducted by genetic algorithm. It is concluded that after optimization total electricity use in Cases 1, 2, 3, and 4 is reduced by 14.9 %, 14.7 %, 14.6 %, and 2.7 %, respectively. Therefore, this study provides a guideline for optimal design of solar-assisted heat pump systems with PCM tank for swimming pool utilization.