The phase transition state and the heat capacity (c(p)) of the binary system of [quercetin (1) + poly(ethylene glycol) 6000 (2)] were measured by a differential scanning calorimeter (DSC). The effect of the mass fraction of quercetin (w(1)) on the melting temperature (T-fus) and enthalpy (Delta(fus)h) were discussed. Experimental results indicate that, for T > 353 K, a molten polymer dispersion is found in the region of w(1) < 0.3; in the region of w(1) > 0.6, the system is of the character of a mixture of solid quercetin + poly(ethylene glycol) (PEG) 6000 dispersion; in the composition region of w(1) from (0.301 to 0.601), a special complex composed of molten PEG dispersion and solid quercetin is found. A polynomial equation with temperature and composition as variables is used to correlate the c(p) data. The mixing functions of enthalpy, entropy, and Gibbs function were calculated from the data of c(p).