The rates and the activation parameters for the reaction of phenacyl bromide with substituted anilines in methanol and dimethylformamide were measured. The effects of substituted anilines were discussed. The rate of the reaction was increased with the electron donating power of substituent and showed larger value in DMF than in MeOH. The isokinetic relationship was shown between ${delta}H^{ eq}$ and ${delta}S^{ eq}$, isokinetic temperature was 539 and $400^{circ}C$ in MeOH and DMF respectively, but p-nitro aniline was deviated from linearity in both solvents caused by solvent effects. The excellent linear relationship between log k and p$K_a$ of substituted anilines was observed by following equation. log k = 0.57p$K_a$-1.28 (r = 0.996) in MeOH at $45^{circ}C$, log k = 0.65p$K_a$-0.88 (r = 0.970) in DMF at $45^{circ}C$. From the Hammett plot, this reaction was a nucleophilic displacement of aniline to phenacyl bromide and the following equation was obtained at $45^{circ}C$. log k/$k_0$ = -2.00${sigma}$ + 0.06 (r = 0.985) in MeOH; log k/$k_0$ = -2.22${sigma}$ + 0.08 (r = 0.995) in DMF. Large deviation of p-nitro aniline in DMF is resulted from solvent effects too. From above results, the substituent effect of this reaction can be described as $S_N2$ mechanism and bond formation more proceeds in DMF relative to MeOH.