The interaction of p-benzoquinone and proline has been studied for many years, but there is much controversy about the product of the interaction. The Resonance Raman spectroscopy produced in liquid core Teflon optical fiber and the UV absorption spectroscopy are applied to investigate the interaction of p-benzoquinone and proline. The experimental results indicate that the pH value of the mixed solutions has crucial effect on the product of the interaction. Varying the pH value leads to three different products: charge-transfer complex, benzosemiquinone radical anion and substituted quinone. The mechanism of the formation of benzosemiquinone radical anion under the condition of strong alkaline has been discussed. And we also develop the continuous variation method for determining the composition of the charge-transfer complex. The study not only clarifies the controversy on the product of the interaction, but also applies the resonance Raman spectroscopy in liquid core optical fibers on detecting amino acids with p-benzoquinone.