For the method of phase transfer catalysis oxidation to synthesize benzoic acid,a series of factors were reviewed in detailed.The catalysis effect of HDTBP was found the best.The yield was 70 1%.BTEA is a good catalyst and cheaper than HDTBP,and its yield was 50 5%.The fact that potassium permanganates decomposition hampered its oxidation to organic substrate was discovered,so the reaction should be done in neutral medium. For the method of phase transfer catalysis oxidation to synthesize benzoic acid, a series of factors were reviewed in detail. The catalysis effect of HDTBP was found the best. The yield was 70% .BTEA is a good catalyst and cheaper than HDTBP, and its yield was 50 5% .The fact that potassium permanganates decomposition hampered its oxidation to organic substrate was discovered so so reaction should be done in neutral medium.