The phase separation kinetics of polystyrene／poly(vinyl methyl ether)(PS／PVME)blends under oscillatory shear was studied on a customized Rheo-SALS tester．It was found that

under fixed frequency and strain amplitude

the phase separation exhibited anisotropy and periodicity．At a given phase angle

the early—stage kinetics of phase separation followed the classical Cabn-Hilliard theory．The average of characteristic wavenumber qm

where the maximum scattering locates

stayed unchanged during the phase separation

implying that only the composition fluctuations with specific size will be favored under a oscillatory shear with given frequency and strain amplitude．Under shear

qxm

the characteristic wavenumber along flow direction

experienced a compulsive oscillation with a frequency same as that of shear

while qzmthe characteristic wavenumher along vorticity direction

dose not．Through simultaneous rheological measurements

it was also found that stress could appropriately reflect the stage of phase separation．For example

the first normal stress difference reached maximum when the early stage of phase separation ended.