The present document discloses a method and a system for determining a delay difference, and a base station and UE, the method includes: a serving cell receiving information of time measured by a neighboring cell at which uplink channel/signal information of UE for determining a synchronization delay is received; and the serving cell determining a synchronization delay difference between the UE to the serving cell and the UE to the neighboring cell according to information of time measured by the serving cell at which the uplink channel/signal information of the UE for determining the synchronization delay is received, and the information of time measured by the neighboring cell and at which the uplink channel/signal information of the UE for determining the synchronization delay is received, wherein the uplink channel/signal information measured by the serving cell is the same as the uplink channel/signal information measured by the neighboring cell.