A bare quartz optical fiber is embedded in a polydimethylsiloxane (PDMS) substrate microfluidic channel, pumped by a continuous wave laser along the fiber axis, and the dye fluorescence excited by evanescent field of the pump beam has been investigated. As the evanescent field of the pump beam is homogeneous along the fiber axis, it is found that the fluorescent emission from the rim of fiber is uniform along the microfluidic channel. The experimental results show that the fluorescent emission intensity strongly depends on the dye concentration and the refractive index of the dye solution, and with the increase of the dye concentration and the refractive index of dye solution, the emitted fluorescent intensity increases accordingly. The observed phenomena have been successfully explained based on the mechanism of evanescent wave pumping fluorescent radiation.