Lipid-polymer composite microspheres (LP-MS) for colon-specific drug delivery were prepared using an ultrasonic spray freeze-drying technique. These microspheres, which consist of the pH-sensitive polymer Eudragit S100 and the non-polar lipid Compritol 888 ATO, were characterized by morphological and physicochemical properties. It was found that the LP-MS have a spherical lipid porous matrix with a smooth pH-sensitive polymer film on both internal and external surfaces, and the insoluble drug 10-hydroxycamptothecin was dispersed in an amorphous state in the carrier. Morphological changes of microparticles under different pH conditions were observed by confocal laser scanning microscopy, which showed that the lipid matrix in LP-MS restricted the swelling property of the polymer at pH 6.8. In drug release studies, less than 15% of the drug was released below pH 6.8, whereas more than 30% was released with a sustained-release model at pH 7.4. The LP-MS could provide a promising vehicle for colon drug delivery.