A GaN blue light emitting diode (LED) integrated monolithically on a Si substrate is used as a fluorescent light source of bio-fluidic micro total analysis system (μTAS) with polydimethylsiloxane (PDMS) channel. A Si photodiode (Si PD) is also installed on a Si substrate for fluorescent detection. Therefore, all basic optical components necessary for fluorescent μTAS are integrated on a Si platform. A GaN LED layer on a Si substrate is micromachined by etching the Si substrate to generate a ring-shaped light source for a dark-illumination optical configuration. The blue emission at the wavelength of 477nm suits the excitation of the fluorescent dye of fluorescein isothiocyanate (FITC). Using the integrated chip, the fluorescent emission form a flowing fluid with the dye is measured as a function of the concentration. The noise, sensitivity and detection limit are evaluated to be 0.57pA, 1.21pA/μM and 469nM, respectively.