Abstract: This paper proposes two types of multi-tank solar assisted air source heat pump hot water systems that add the heat storage tank at night and the buffer tank of the heat pump unit,and designs optimal operation strategies in each case,with the goal of improving the hot water system of university dorms’ economic benefit and emission reduction effect. The parameters such as water tank volume,collector area,tilt angle,and heat pump power are chosen as optimization variables,and the annual value of life cycle cost and the annual carbon emissions of operation are computed as the objective function. By research and analysis of the monthly power consumption,electricity cost,hot energy guarantee rate,and average power COP of the single water tank,double water tank,and three water tank solar water system,it is discovered that the three water tank solar water system can lpower consumption by about 3.86%,save electricity cost by 22.35%,increase solar energy guarantee rate by 33.32%,increase average system COP by 45.70%,reduce life cycle cost by 5.07%,reduce carbon emissions by 3.72%,and increase exergy efficiency by 4.65%.