The invention discloses a synthesizing method of a pesticide intermediate 1-methylcyclohexanecarboxylic acid. The 1-methylcyclohexanecarboxylic acid is prepared by taking 2-methylcyclohexanol, formic acid and an R-Cl halogenating reagent as the raw materials through halogenation and substitution reactions by means of a one-pot method. The synthesizing method is novel, the defects in a traditional production process can be overcome, emission of waste acid water is reduced, the production capacity is enlarged, and the synthesizing method is green and environmentally friendly.