A phase locked loop and an associated alignment method are provided. A disclosed phase locked loop receives a reference signal to provide a feedback signal. The phase locked loop is first opened. When the phase locked loop is open, a frequency range of an oscillating signal from a voltage-controlled oscillator is substantially selected. The feedback signal is provided according to the oscillation signal. After the frequency range is selected, the phase locked loop is kept open and the phases of the reference signal and the feedback signal are substantially aligned. The phase locked loop is then closed after the reference signal and the feedback signal are aligned.