A high current radio frequency quadrupole (RFQ) is being studied at the Institute of Modern Physics,Chinese Academy of Sciences (IMP,CAS) for the direct plasma injection scheme (DPIS).Because of the strong space charge of beams from laser ion source,the beam dynamics design of the RFQ has been carried out with a new code,which can deal with space charge effectively.The design of the RFQ structure is performed with an electromagnetic simulation code and the determination of parameters of the structure has been done to maximize the shunt impedance when the frequency is kept fixed.The influences of dipole mode effect and flatness on beams were also discussed.