The solid-layer growth kinetics and resulting crystal purity for a well-mixed p-xylene (PX) melt with impurity of o-xylene (OX) or ethylbenzene (EB) were studied in this work at various cooling temperatures. A correlation based on the energy balance was adopted to describe the dependence of growth rate on the temperature gradient between melt and cooling medium. An empirical equation based on the mass balance was proposed to relate the effective distribution coefficient with growth rate, mass transfer coefficient, and impurity mole fraction. By fitting the proposed empirical equation with the experimental effective distribution coefficients, the mass transfer coefficients for the PX/OX and PX/EB mixtures were retrieved respectively.