The invention discloses a single detector X-ray pulsar navigation time-sharing observation method and device, wherein the method comprises the steps: obtaining a system transcendental state and a system transcendental state covariance; according to a measurement equation and a measurement error estimation value of each to-be-observed X-ray pulsar in a preset database, the system transcendental state and the system transcendental state covariance, obtaining a forecasted system posteriori state covariance; according to the forecasted system posteriori state covariance, calculating a system state posteriori estimation error corresponding to each to-be-observed X-ray pulsar, to select an X-ray pulsar with minimal system state posteriori estimation error for observation; observing an X-ray pulsar with the minimal system state posteriori estimation error to obtain the arrival time of an X-ray pulsar signal, so as to update a measurement value; and according to the updated measurement value, obtaining a system posteriori state and a system posteriori state covariance matrix. The method can effectively improve the navigation accuracy by using the time-sharing observation.