Abstract: Disclosed are a use of a methylacryloyl benzimidazolone derivative, an optical isomer or a pharmaceutically acceptable salt or prodrug thereof in the preparation of: (a) a pharmaceutical composition or reagent for down-regulating the activity of PI3K/Akt pathways; (b) a pharmaceutical composition or reagent for treating or inhibiting a tumour; and/or inhibiting tumour cell growth; and/or (c) a pharmaceutical composition or reagent for blocking the cell cycle. The compounds involved in the present invention can down-regulate the level of Akt phosphorylation in P13K/Akt signaling pathways, and the functional effects of the compounds are equivalent to those of a novel small-molecular targeting drug MK2206; while the research at the cellular level has found that the methylacryloyl benzimidazolone derivatives represented by FD1 have a good proliferation inhibiting effect on tumour cells. What is different from MK2206 is that FD1 has better effects on a PTEN deleted cell.