The invention discloses a microporous polymer-nano-metal particle catalyst and especially relates to a microporous polymer-nano-palladium catalyst and a preparation method thereof. The preparation method comprises that prepared bromine-substituted triarylimidazole group-containing monomer 2, 4, 5-tris(4-bromophenyl)-1-alkylimidazole (TAI) undergoes a reaction to produce a microporous polymer, the microporous polymer is dissolved in DMF, and an appropriate amount of a H2PdCl4 aqueous solution is added into the DMF solution and undergoes a reaction, and excess NaBH4 is added into the reaction product so that the microporous polymer-nano-metal particle catalyst is obtained. The microporous polymer has high nitrogen content, has a multi-pore structure and helps to increase the loading amount of the transition metal. The catalyst has strong catalytic activity, good selectivity, mild reaction conditions, good reusability and a good market application value.