The invention discloses an automatic water supplying and breaking system of a solar water heater. A water level signal acquisition device (6) of a floating ball (2) with an iron block inside is mounted on a water tank overflow pipe (14) and externally provided with a main oscillation coil (3) and a tickler coil (4). The two coils, an inductive feedback high-frequency oscillator (102), a micro-control signal processor (9), a relay (10) and an electromagnetic valve (7) are sequentially connected, and the electromagnetic valve (7) and the other electrode of the relay (10) are connected with a 220V mains supply. By the aid of the automatic water supplying and breaking system, automatic water supplying and automatic water breaking in case of water overflowing are realized. As the coils are free of contact with water, the automatic water supplying and breaking system of the solar water heater is long in service life and reliable in working, and performance of the solar water heater is effectively improved. The automatic water supplying and breaking system can be provided to manufacturing factories of the solar water heaters to be mounted on products before leaving the factories and can be mounted on used products, so that both old and new customers are facilitated. The automatic water supplying and breaking system has the advantages of simple structure, convenience in operation, high practical value and marketing prospect.