The invention discloses a sizing agent for emulsion type carbon filter and a preparation method and application thereof. The sizing agent is prepared by 2-40% of epoxy resin, 1-20% of modifiers, 0-96.5% of water and 0.5-15% of surfactant. After the carbon fiber sized by the sizing agent is prepared into a polyamide, polyimide or polyetherimide resin-based carbon fiber composite material, as the sizing agent comprises the modifiers which have similar or same structural units with matrix resin in the carbon fiber composite material, stronger interface bonding forces exist between the carbon fiber and a sizing agent layer and between the sizing agent layer and the thermoplastic matrix resin; the carbon fiber is effectively combined with the thermoplastic matrix resin through a sizing agent transitional connecting layer so as to form an organic whole; and compared with current carbon fiber composite material, the interlaminar shear strength is improved by over 20%, so that the carbon fiber composite material is higher in integral performance.