The invention relates to a method for calculating kerogen density in a rock. The method can calculate density values of kerogen I, II, III and IV and any type of mixed kerogen. The method mainly comprises measuring bulk density and true density of a rock sample, carrying out pyrolysis analysis to obtain the TOC content of the rock sample and the carbon content of kerogen, and carrying out calculation according to a calculation formula of the invention. The method can fast and accurately calculate kerogen density and is helpful to the study of seismic petrophysics.