A method for detecting optical signals, a microfluidic mixing chip having light emitting compound and a system thereof are provided. The microfluidic mixing system comprises the microfluidic mixing chip, an electrode pairs and a power supplier. The microfluidic mixing chip comprises a first side cavity, a second side cavity and a mixing cavity. The mixing cavity is disposed between the first side cavity and the second side cavity. The mixing cavity further contains the light emitting compound, a catalyst and a redox reagent. The electrode pair is respectively disposed to the first side cavity and the second cavity. The power supplier supplies a power source with high frequency alternating current electric field. By utilizing the power source with alternating current electric field, the light emitting compound, the redox reagent and the catalyst are mixed in the mixing cavity to generate a chemiluminescence or bioluminescence optical signal to detect.