Abstract: MWW zeolites is an important catalyst in petrochemical industry. However, the efficient preparation of MWW zeolites still faces challenges, and the origin of influential factors for regulating its structure properties also remains obscure. Herein, we designed a nanoscale amorphous silica-alumina species denoted as active precursor (APS), and adopt the APS in the HMI mixture to synthesize MCM-22 zeolite (APS-MWW) successfully. To reveal the distinctive role of APS in promoting the crystallization of MWW zeolites, two crystal materials (ITQ-1 and MCM-22) and one mother liquor (ML) as seeds to synthesize three types of MWW zeolites. Typically, when adding APS in the synthetic mixture, the HMI amount was reduced to less than a quarter and crystallization time was reduced to 36 h. APS-MWW sample provides a smaller particle size (2–4 μm) and thinner stacked layer thickness (5–20 nm). Synchrotron radiation Small Angle X-ray Scattering (SAXS) shows each seed has a different impact on the species’ fractal structure and size distribution in the mixture, which is highly related to the nucleation and growth of MWW zeolites. APS shows a large number of 6 membered ring (MR) structure units which play a significant role in boosting the rapid nucleation and growth of APS-MWW zeolite. Among the synthesized MWW zeolites, the APS-MWW performs the highest ethylbenzene yield in the alkylation reaction of benzene-ethylene, which is attributed to its moderate flake thickness, appropriate texture properties and more external surface acidity. The results will provide a new perspective for producing MWW-types zeolites by using the available and effective active precursor.