The invention relates to a hybrid optical pumping-based accurate atomic density measurement method. The method comprises the steps of heating an alkali metal gas chamber filled with K and Rb up to starting temperature, and measuring to obtain laser absorption spectrums of the K and the Rb to obtain densities of the K and the Rb at the starting temperature, and associating Raoult's law to obtain the starting temperature as well as ratios of saturated vapor pressures to molar fractions of the K and the Rb at the starting temperature; heating the gas chamber up to working temperature, wherein the density of the Rb is very high and the absorption is very strong near a resonance point in an SERF state, carrying out curve fitting to obtain a greater deviation of the density of the Rb, and accordingly obtaining the density of the K by means of a spectral absorbing method; combining the known molar fraction of the K, and calculating to obtain the working temperature; combining the molar fraction of the Rb to obtain the saturated vapor pressure of the Rb at the working temperature, and further obtaining the density of the Rb at the working temperature. The hybrid optical pumping-based accurate atomic density measurement method is suitable for the situation that during hybrid optical pumping, the saturation absorption spectrum is very high in atomic number density and is very strong in absorption at the both sides of a resonant peak, so that the density is difficult to obtain by means of a fitted curve.