A delay tracking method and a memory system are provided. The delay tracking method is applied to a memory system supporting a low-frequency-mode (LFM) and a high-frequency-mode (HFM) of an operating clock. The delay tracking method includes the steps of selecting a LFM oscillator for obtaining a LFM delay value when the operating clock is in the HFM; and selecting a HFM oscillator for obtaining a HFM delay value when the operating clock is in the LFM.