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Disturbance of atactic polystyrene (aPS) networks on the polymorphism transitions ofsyndiotactic polystyrene (sPS) was studied by using in-situ wide angle X-ray diffraction (WAXD) anddifferential scanning calorimetry (DSC). Two series samples of solvent induced sPS crystals in aPSnetworks were prepared, one formed in aPS gel (sPS/aPSNW1) and the other formed in aPS solutionand thereafter fixed by cross-linked aPS chains (sPS/aPSNW2). For comparison, SPS blends with linearaPS (sPS/aPS) were also prepared under the same conditions. The sPS clathrate (δ ) form crystal wasobtained in all samples. The δ form of sPS transforms into γ form and then into α form with a lowerheating rate, while the δ form of sPS transforms directly into β form with a higher heating rate. But, thepresence of aPS networks was not favorable for the formation of β form of sPS. When annealed the sPSδ form samples at a temperature above 150°C, aPS networks in both sPS/aPSNW2 and sPS/aPSNW1retard the transformation of dform into β form, but improve the transition of dform into γ form and then into α form. Moreover, aPS networks were also not favorable for the formation of β form of sPSfrom melt-crystallization, but for α form. It shows that the presence of aPS networks disturbs the sPSmodifications and is not favorable to the formation of sPS β form during polymorphism transitions.