The invention discloses a transition metal phosphide/porous carbon anode composite material for a sodium-ion battery and a preparation method thereof. The composite material is formed by dispersive distribution of transition metal phosphide nano-particles in a porous carbon material. A preparation process of the composite material comprises the following steps of preparing a transition metal organic frame structure by transition metal salt and organic ligands through an in-situ growth method; respectively placing the transition metal organic frame structure and a phosphorus source on two ends of a tube furnace, heating the tube furnace, and meanwhile, circulating liquid inert gas into one end of the tube furnace with the inorganic phosphorus source to carry out heat treatment; and washing and drying a heat treatment product in sequence to obtain the composite material. The prepared transition metal phosphide/porous carbon anode composite material used as the anode material of the sodium-ion battery has high specific capacity, good rate capability, simple preparation method, low cost and wide industrial application prospect.