Covalent organic frameworks (COFs) are emerging as crystalline porous materials for advanced membranes, due to their regular pore structures and high porosity. The fabrication of defect-free ultrathin COFs membranes is still very challenging, since the poor COF-substrate affinity hampers the nucleation of COF crystallites. In this work, a facile direct growth method was developed to deposit continuous imine-based COF layer (TpPa-1, synthesized by the Schiff-base reactions of 1,3,5-triformylphloroglucinol (Tp) with p-phenylenediamine (Pa-1)). Aldehydes groups were firstly immobilized on polyacrylonitrile (PAN) porous substrate as the nucleation sites to promote the growth of continuous TpPa-1 layer via a good COF-to-substrate adhesion. Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and X-ray diffractometer (XRD) confirmed the formation of COF layer. The TpPa-1/HPAN membrane exhibited high water flux of 418.5 L/(m(2)h MPa) under the operation pressure of 0.1 MPa and excellent dyes rejection (93.91% for Orange GII and over 99% for Methyl blue, Congo red and Alcian blue). The high separation performance, coupled with its facile fabrication and remarkable stability, may render imine-based COFs membrane promising for wastewater treatment.