A direct filtering type switching power supply, applied to occasions comprising pulsating direct currents, comprises a filter circuit (200), a main power level (300), and an indicating circuit (400). The indicating circuit (400) comprises a terminal (1, 2), a resistor (R1), a capacitor (C1), a diode (D1), and a light-emitting diode (LED). The LED and the D1 are reversely connected in parallel, then are connected in parallel to the R1, and then are serially connected to the C1, and the indicating circuit (400) and a filter electrolysis device CL are connected in parallel. The capacity of the C1 is small, a current of the great power frequency ripple caused by rectification and passing through the C1 is very small, and a voltage drop generated on the R1 is insufficient to light the LED; as the ESR of the CL increases, a voltage drop generated on the ESR by a high-frequency excitation current synchronously increases, and accordingly a formed high-frequency ripple voltage increases; the C1 has a high-frequency switching-on effect, and when the high-frequency ripple voltage on the ESR reaches a threshold, the LED is lit and emits light, and the threshold can be adjusted by adjusting the resistance of the R1. In this way, a user is reminded that the ESR of the electrolysis device CL has increased, and the switching power supply has the risk of ineffectiveness. The circuit has low costs and is easy to implement, and does not use inductance detection.