A light-emitting device with open-loop control including a LED capable of emitting a blue light and a mix-light adjusting portion is provided. The mix-light adjusting portion includes a first and a second fluorescent material both capable of being excited by blue light. When the first and the second fluorescent material are excited by a short-wavelength blue light, the excitation intensity of the first fluorescent material is higher than that of the second fluorescent material. When the first and the second fluorescent material are excited by a long-wavelength blue light, the excitation intensity of the first fluorescent material is lower than that of the second fluorescent material. The peak wavelength of the emission of the first fluorescent material is smaller than that of the emission of the second fluorescent material. The dividing wavelength between the short-wavelength blue light and the long-wavelength blue light ranges from a first to a second wavelength.