The invention discloses a WC polycrystalline foamed ceramic catalyst. The WC polycrystalline foamed ceramic catalyst comprises the following components in percent by mass: 60-70% of WC, 2-5% of Ni, 5-10% of Al, 10-15% of Si, 15-25% of Zn, 20-30% of NH4<+> and the balance of (C6H10O5)n. The invention further discloses a preparation method of the WC polycrystalline foamed ceramic catalyst. The preparation method comprises the following step: adding WC, nickel nitrate, pseudo-boehmite, silica gel, basic zinc carbonate, ammonium hydrogen carbonate and starch into a powder mixer for a mixed reaction. The invention further discloses a method for catalyzing waste plastic and biodiesel to produce hydrocarbon by using the WC polycrystalline foamed ceramic catalyst. The method comprises the following step: with the waste plastics as a hydrogen donor, the WC polycrystalline foamed ceramic catalyst as a hydrodeoxygenation and isomerization catalyst and a TiO2 polycrystalline foamed ceramic catalyst as a catalytic reforming catalyst, catalyzing conversion of the biodiesel into liquid hydrocarbon fuel through a hydrodeoxygenation and isomerization reaction.