Abstract: A review of the research on clocking effect in turbomacinery in recent years is presented in the paper.As the experiments showed,the benefit acquired by clocking effect in turbine is prominent,and the benefit increases with the flow velocity in compressor.It is believed and interpreted in this paper that the difference of efficency induced by clocking effect results in the unsteady interaction.The introduction of clocking effect is meaningful that this phenomenon gives the way which leads us to use the unsteadiness of flow and urges people to consider function of the flow unsteadiness in the design of turbomachine.An engineering model to make use of clocking effect based on the present understanding of this phenomenon also has been given.