Cochlodinium polykrkoides(C. polykrikoides) is one of the most harmful red tide dinoflagellates due to its great economic damage and compromising recreational opportunity and public health. Titanium dioxide ($TiO_2$) is known to be used as a photocatalyst for the control of the aquatic invasive algae under natural and artificial light. The purpose of this study was to design a highly efficient continuous photocatalytic reactor with $TiO_2$-coated alumina for the demonstrated efficient degradation of C. polykrikoides. $TiO_2$ photocatalyst beads were prepared by sol-gel dip-coating method using titanium tetra iso-propoxide on alumina. After 40 min of ultraviolet illumination time, the reduction of C. polykrikoides cell number was more than 80%. The degree of degradation of C. polykrikoides increased in a time-dependent manner in this novel reactor. The degradation begins with photocatalytic action by the oxidative species of $TiO_2$ on the protective cell structures of C. polykrikoides.