This paper developed a new design of variable swirl intake manifolds for four-valve DI diesel engine by setting swirl control valves in the intake manifolds. The 3-D numerical model under the same experimental condition was established and particular flow information in intake manifolds and cylinder was achieved. Influence of variable swirl intake manifolds on intake flow characteristics and in-cylinder swirl characteristics were analyzed. The simulation results show that the swirl intensity in cylinder can be tuned by this device. The swirl intensity increases gradually with decrease flow coefficient and it can meet the requirements of swirl intensity for different operating conditions.