The utility model discloses a horizontal solar water heater. A group of solar vacuum glass tubes outside a water storage tank are communicated with a group of metal heat transfer tubes in the water storage tank to form a closed loop, and heat conduction fluid is poured into the closed loop; the solar vacuum glass tubes and the heat conduction fluid are heated through sunlight; the heat conduction fluid circularly flows in a closed pipeline through the characteristics that liquid floats up when the temperature is raised and sinks when the temperature is reduced and the temperature difference between the interior of the water storage tank and the solar vacuum glass tubes; water in the water storage tank is continuously heated, and the metal heat transfer tubes can also rapidly heat the water, so that the water heater is high in heat transfer efficiency; water does not flow inside the vacuum glass tubes, so that the water heater is good in sealing performance, prevents tube explosion, and can be operated under pressure; water is thoroughly isolated from a rubber ring and thermal insulation material, so that the water heater achieves edible sanitation, and the purpose of the water heater is enlarged; the water heater does not need a bracket, is small in size, low in weight, low in cost, and convenient to transport and install, can be directly laid on the ground, and is high in installation density and convenient for being mounted on a wall; the water heater has ultra-large capacity, and the use amount is greatly increased; the water heater has a simple structure, and is produced and machined through common technical equipment, low in investment, rapid to start and short in period.