Blood separation is the first step for subsequent blood tests in clinical diagnosis. Lab-on-a-chip technology provides an automatic, cost-effective and fast solution for a wide variety of blood analyses. The objective of this work is to design a new lab-on-CD microstructure capable of separating blood cells from the whole blood into different reservoirs directly. A CD platform including a microchannel network consisting of a straight main microchannel, a curved microchannel and a branching microchannel has been proposed. The merits of this design are its simple structure, less operating time and high separation efficiency because it utilizes multiple separation mechanisms, for instance, two centrifugal forces and Coriolis force. One centrifugal force is due to the system rotation; the other centrifugal force is due to the curvature of the specifically designed curved channel. In this work, systematical evaluation on the functionality and performance of such a design has been done. Ninety-nine per cent separation efficiency is achieved for diluted blood of 6% hematocrit.