A method and apparatus for determining PET scanning time are provided. According to an example of the method, a CT image is divided into multiple single-bed CT images according to bed information of bed positions for a PET scan, wherein the CT image is obtained by performing a CT scan on a subject of the PET scan, and a one-to-one corresponding relation exists between the multiple single-bed CT images and all of the beds. A residual true coincidence count ratio is estimated for each of the beds based on corresponding single-bed CT image of the bed, and then a scanning time proportion for each of the beds may be determined based on each of the residual true coincidence count ratios for the beds.
