A single stage low boost/buck ratio stand-alone solar energy power generating circuit with a system thereof is a simplification of a two-stage type circuit. The two-stage circuit, which has a storage unit, a charging converter circuit for charging the storage unit, and a discharging converter circuit for discharging the stored power to a load, is analyzed and categorized such that a circuit structure is selected via a suitable simplified combination to commonly use the elements constituting the charging and the discharging converter circuits so as to form the single stage circuit with less elements, volume and weight for reducing the production cost of the circuit.