The invention discloses a method of extracting benzoic acid, benzaldehyde and methylbenzene from a toluene oxidation reaction liquid and belongs to a separation method of the toluene oxidation reaction liquid. The method includes following steps: 1) feeding the toluene liquid-phase oxidation reaction liquid into the bottom of a first rectifying column, and heating the reaction liquid when the liquid level reaches 1/3-1/2 of the bottom of the first rectifying column; (2) when the apparatus reaches total reflux, feeding vapor for controlling the temperature of the bottom of the first rectifying column to be 250-260 DEG C and the temperature of the bottom of the first rectifying column to be 185 DEG C; (3) feeding the top discharged material from the first rectifying column into the middle-lower part of a second rectifying column, and controlling the temperature of the bottom of the second rectifying column to be 177-180 DEG C and the temperature of the bottom of the second rectifying column to be 110-112 DEG C; and (4) through a continuous middle material feeding method, withdrawing a material flow from the bottom of the first rectifying column to obtain the benzoic acid, withdrawing a top distilled substance from the top of the second rectifying column to obtain the methylbenzene, and withdrawing a material flow from the bottom of the second rectifying column to obtain the benzaldehyde. The method is short in separation period, is simple in operation, is low in energy consumption and is high in yield. The obtained benzoic acid is high in purity. The method can achieve industrialization of extraction of the benzoic acid, the benzaldehyde and the methylbenzene from the toluene oxidation reaction liquid.