A projection method and system, and an electronic device are provided. In this method, a user can drag a projection window in a remote device to a local device. For example, the user may drag the projection window in the remote device to the local device by using a mouse. The user may drag the projection window from the local device to the remote device. The user may adjust, on the local device, a size of the projection window displayed on the local device. In the technical solution provided in this application, a user operation is simple during projection.