The invention discloses a method and a device for measuring colors of a liquid crystal screen. The method comprises a ray collection and filtering step, a photovoltaic conversion and analog-to-digital conversion step, a data storage and entropy value processing step and a stability judgment step. According to the method and the device for measuring the colors of the liquid crystal screen, provided by the invention, optical data of the liquid crystal screen is acquired through an optical sensor; before brightness is output, the stability of current data is judged; after the stability of the liquid crystal screen is determined, a brightness value is output. The judgment of the data stability is analyzed and judged according to an entropy value of acquired data, so that a condition that erroneous judgment is caused by instable data can be avoided in detection and adjustment process of an automatic production line of the liquid crystal screen; the automatic adjustment time is shortened and the working efficiency is improved.