1. A light-measuring method for measuring a to-be-measured light by a light-measuring system according to a look-up table comprising a plurality of spectrum parameters and a plurality of look-up color coordinates based on a light spectrum model, each look-up color coordinate corresponding to one of the plurality of spectrum parameters, the light-measuring method comprising the following steps of: measuring the to-be-measured light by the light-measuring system, for obtaining the actual stimulus values, and then calculating an actual color coordinate; determining at least one of the look-up color coordinate matched with the actual color coordinate according to the actual color coordinate and the look-up table; and determining a to-be-measured light spectrum parameter according to at least one of the spectrum parameters of at least one of the matched look-up color coordinates.