The invention discloses a device for measuring blue light weighted radiation intensity and a method thereof, wherein the device for measuring the blue light weighted radiation intensity comprises a testing system and a sighting system, the testing system comprises an objective lens, a perforated mirror, a lens, a first dispersion element, an attenuation slice, a second dispersion element and a photovoltaic cell, the photovoltaic cell is connected with a voltmeter, the objective lens, the lens, the first dispersion element, the attenuation slice, the second dispersion element, a photovoltaic center of the photovoltaic cell, a hole of the perforated mirror and a light source are arranged on a same optical shaft, the attenuation slice is closely fit on the second dispersion element, the sighting system orderly comprises an objective lens, a reflecting mirror, a delay lens group, a cursor and an eyepiece, reflecting rays of the perforated mirror are sent to the reflecting mirror, the reflecting rays of the reflecting mirror are sent into the eyepiece through the delay lens group and the cursor, and the objective lens, eyes and photovoltaic cells are conjugate. The device for measuring blue light weighted radiation intensity and the method thereof are simple in structure, small in volume, light in weight, convenient to use, rapid in response speed, cheap in price and small in technical difficulty, and are suitable to be used in indoor and outdoor various occasions and the like.