I will review the large scale structure study with QSO Ly-alpha absorption spectrum. It is generally believed that the underlying cosmic mass field traced by QSO Ly-alpha absorption spectra are weakly clustered, or pre-clustered. However, the QSO Ly-alpha absorption spectrum not only contains valuable information about linear mass density perturbations, but also about the non-linear clustering regime, and the intermittent and singular behavior of the cosmic mass field. Thus, QSO Ly-alpha absorption plays an unique role of discriminating among models of structure formation.

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