This disclosure relates to a pulse oximeter. The pulse oximeter includes a light source； a light acquirer spaced apart from the light source； a processor connected to the light acquirer； a filter in the light path from the light source to the light acquirer； and a first mechanical device. The filter includes a first single band filter having center wavelength of 660 nm and a second single band filter having center wavelength of 940 nm. The first mechanical device moves the filter so that the first single band filter and the second single band filter are alternately in the light path from the light source to the light acquirer. The double band filter can filter the unnecessary light and improve the accuracy of the pulse oximeter.
