Time-resolved techniques are widely used in measuring the spectra and lifetimes of the excited states of molecules. However, the relative apparatus always requires gated detector and phase-matching circuitry, which is expensive to implement and maintain. Herein, a novel auto-phase-locked method for time-gated luminescence (TGL) spectra measurement was developed by adjusting the exciting and detecting optical paths to pass through the same chopper wheel, which simultaneously acted as a pulse generator and detecting shutter. This low-cost system needs no phase-matching circuitry or control system. It can detect TGL spectra with a delay time of only microseconds, demonstrating a high temporal resolution for thermally activated delayed fluorescence detection.