The isotatic polypropylene (iPP layer, denoted as A)/β-nucleating agent filled-isotatic polypropylene (β-PP layer, denoted as B) alternating multilayer composites were prepared through layer-multiplying extrusion combined with an assembly of layer-multiplying elements (LMEs). A and B were extruded from different extruders and combined as a 2-layer melt in the coextrusion block, then flowed through n LMEs forming 2n+1 layers like A(BA)nB. The content of β-crystal was firstly evaluated by differential scanning calorimetry (DSC), which indicated that the relative amount of the β-crystal increased from 38.67% to 81.22% with the increase of layer numbers from 2-layer to 128-layer. It was well consistent with the results of X-ray diffraction (XRD). The morphology of β-crystal was also investigated by hot stage optical microscope(H-S POM). It was revealed that the β-PP layer could induce numerous fan-shaped β-transcrystallinity in the interface between pure iPP layer and β-PP layer. Since the crystallization temperature of β-PP was 10°C higher than the crystallization temperature of iPP, the iPP layer could be almost induced to β-transcrystallinity in the interface instead of forming α-crystal. The high content of β-transcrystallinity could also be largely obtained by reducing the thickness of β-PP layer and further improving the crystallization temperature of β-PP due to the faster completion of crystallization process. The non-isothermal crystallization kinetic analysis via Mozhishen’s methods demonstrated that the crystallization rate was greatly enhanced by the augment of the interface. It was suggested that layer-multiplying extrusion was beneficial to achieve higher content of β-crystal.