An annular optical shifter and a method for controlling shift, where the annular optical shifter includes: a first bent straight-through waveguide, connecting an input end and an output end of an optical signal, and configured to transmit, to the output end, the optical signal input from the input end; multiple optical delay waveguide loops, arranged transversely and parallel on two arms of the first bent straight-through waveguide, where the multiple optical delay waveguide loops are configured to temporarily store optical signals; multiple pairs of optical switches, where each pair of optical switches are configured to control on and off of an optical path that is on the two arms of the first bent straight-through waveguide and two sides of an optical delay waveguide loop corresponding to each pair of optical switches; and a controller, configured to implement shift-up or shift-down of the optical signals.