The invention belongs to the field of pesticide production waste water treatment and discloses a 2,4-D pesticide production waste water pretreatment method. 2,4-dichlorophenol and 2,4-D are recovered from the waste water by a liquid membrane separation technique, so harmful pollutants are removed and reclamation is realized at the same time. The 2,4-D pesticide production waste water pretreatment method mainly comprises the following steps of: 1) preparing emulsion; 2) performing liquid membrane extraction; and 3) breaking the emulsion. The 2,4-D pesticide production waste water pretreatment method particularly comprises the following steps of: preparing the emulsion by cutting an oil phase comprising a surfactant, an additive and a membrane solvent and aqueous solution of sodium hydroxide at a high speed; dispersing the emulsion to 2,4-D pesticide waste water to perform extraction; allowing the 2,4-dichlorophenol and the 2,4-D to enter a liquid membrane phase; breaking the emulsion electrostatically to generate 2,4-dichlorophenol sodium salt and 2,4-D sodium salt; and applying to a condensation section of the product, wherein after the pretreatment, the removing rate of phenol and the 2,4-D in the waste water is over 99 percent, COD removing rate is over 57 percent and biochemical property is achieved. By the method, the 2,4-D pesticide production waste water can be discharged stably and standardly; and remarkable environmental, economic and social benefits are achieved.