The unsteady surface pressure on stator blade of an axial compressor was measured by means of mounting micro-sensors onto blades surface.The unsteady blade surface pressure was analyzed.There are different factors to play decisive roles on the unsteady surface pressure and unsteady force with the decrease of flow coefficient.Before stall

unsteady blade surface pressure depends on the wake and potential perturbation of adjacent blade row.But after stall

unsteady blade surface pressure depends on the stall cells.Before stall

maximum amplitude of unsteady blade surface pressure and unsteady force occurs at the flow coefficient of maximum total pressure rise.However

after stall

the amplitude of unsteady surface pressure and unsteady force will be much greater than at the maximum total pressure rise.On the other hand

the frequencies of unsteady surface pressure and unsteady force change with the decrease of flow coefficient.Before stall

the dominant frequencies are represented by blade-passing frequency and its harmonics

but after stall

the dominant frequencies are represented by stall cell passing frequency.