We demonstrated a facile method to prepare photoluminescent graphene quantum dots using commercial polyacrylonitrile(PAN) based carbon fibers(CFs) as the raw material by facile chemical oxidation and exfoliation method. The as-prepared GQDs with uniform size exhibit an excitation-independent photoluminescence behavior, which is similar to other semiconductor quantum dots. Moreover, when acting as catalyst the uniform GQDs have better activity for electrochemical oxidation of dopamine(DA) than graphene oxides(GOs). The square wave voltammogram(SWV) peak values of GQDs are in good correspondence with DA concentrations and can act as a sensor of DA. We demonstrated a facile method to prepare photoluminescent graphene quantum dots using commercial polyacrylonitrile (PAN) based carbon fibers (CFs) as the raw material by facile chemical oxidation and exfoliation method. The as-prepared GQDs with uniform size exhibit an excitation-independent photoluminescence behavior , which is similar to other semiconductor quantum dots. Moreover, when acting as catalyst the uniform GQDs have better activity for electrochemical oxidation of dopamine (DA) than graphene oxides (GOs). The square wave voltammogram (SWV) peak values ​​of GQDs are in good correspondence with DA concentrations and can act as a sensor of DA.