A pulse radar ranging apparatus and a ranging algorithm thereof are provided. The pulse radar ranging apparatus includes a radio frequency pulse generator, a radio frequency filter, a radio frequency switch and a transceiver aerial. The radio frequency pulse generator generates a pulse signal. The radio frequency filter receives the pulse signal and generates a high-pass filter signal, wherein the high-pass filter signal includes a radio frequency pulse reference signal. The radio frequency switch controls an output of the radio frequency pulse reference signal. The transceiver aerial transmits the radio frequency pulse reference signal. The radio frequency pulse reference signal contacts an object and generates a return signal, and the transceiver aerial receives the return signal. The ranging algorithm processes and analyzes the signals obtained by the pulse radar ranging apparatus, and calculates a distance between pulse radar ranging apparatus and the object by using polynomial interpolation.