The invention discloses SiC nanometer solar energy absorbent applied to a solar water heater. The SiC nanometer solar energy absorbent is prepared from medium water, a pH conditioning agent, nanometer powder and a dispersing agent. The solar water heater comprises a transparent vacuum glass box used for containing the prepared solar energy absorbent, heat conduction water pipes and feeding openings, and slurry of the prepared solar energy absorbent is added to the glass box; sunlight penetrates through the vacuum glass box and irradiates into the slurry, nanometer particles dispersed in water efficiently absorb the sunlight through the surface effect of the nanometer particles, and water temperature is raised rapidly. BY means of the SiC nanometer solar energy absorbent, the problems that in the prior art, invalid wave-absorbing gap positions exist among vacuum pipes, surfaces of inner pipes of the vacuum pipes are provided with selective wave-absorbing materials in an evaporation manner, solar energy absorptance is low, the utilization rate is low, the evaporation process is complex, the cost is high, heat dissipation is high in speed, and the heat insulation effect is poor are solved. Efficient absorption and utilization of solar energy are achieved, the absorption and utilization rate reaches 85-95%, the accomplishment process is simplified, and the cost is low.