The invention discloses a switching power supply improving the light load frequency. The power supply comprises a battery, a DC-DC converter chip, resistors R1 to R7, non-polarity capacitors C1 and C2, a polarity capacitor C3, a field effect transistor Q1, an inductor L1 and diodes D1 and D2; a current detection pin of the DC-DC converter chip can obtain a relative low voltage after voltage dividing by the resistor R2 and R3, the DC-DC converter chip identifies the voltage as that the switching power supply is in a heavy load state, the working frequency is improved, a driving pin of the DC-DCconverter chip outputs a PWM signal to control an output voltage, and a voltage feedback pin is combined to control the output voltage in an ideal state. Thus, the defect that a present boost circuitis too low in frequency during light load is overcome effectively, the inductance amount of the inductor is reduced greatly, the inductor has a lower requirement for the size, circuit design is smaller and higher in efficiency, and the cost is lower.