Polyolefin resin pre-expanded particles having two fusion peaks on DSC curve wherein the proportion of the heat of fusion Qh of the peak appearing on the high temperature side based on the total heat of fusion of the two peaks represented by the equation: [Qh/(Ql+Qh)]×100 falls within the range of 10 to 60% in which Ql is the heat of fusion of the peak appearing on the low temperature side, and the standard deviation of said proportion is not more than 1.2. The pre-expanded particles are prepared by releasing an aqueous dispersion of resin particles impregnated with a blowing agent from a vessel into an atmosphere of lower pressure than the inner pressure of the vessel to expand the particles, while stepwise or continuously raising the inner temperature or the inner pressure of the vessel at a specific rate, and can be molded with stable molding cycle to give cellular molded articles having stable dimensions.