The invention discloses a crude oil saturation obtaining method and device. The method comprises the steps of acquiring a rock core three-dimensional image obtained by conducting three-dimensional reconstruction on a rock core; Adjusting the three-dimensional image of the rock core according to the initial scanning position of the rock core mapped by the three-dimensional image of the saturated water rock core, the three-dimensional image of the saturated water rock core being obtained by performing the three-dimensional reconstruction on the rock core in a water saturation state; Respectivelyobtaining framework space information corresponding to a rock core framework and pore space information corresponding to rock core pores from the saturated water rock core three-dimensional image andthe rock core three-dimensional image obtained through adjustment; And calculating the crude oil saturation of the rock core according to the obtained skeleton space information and the pore space information. By adopting the method provided by the invention, the distribution conditions of rock, crude oil and water of the rock core in different experiment stages can be obtained.