Using the two-component model with the mixing of itinerant carriers and nearly localized carriers with negative -U correlation we study the Josephson effect along c-axis on YBCO/Pb junction.In this model the itinerant carriers have s-wave symmetry and smaller energy gap.The nearly localized carriers have d-wave symmetry and its critical temperature establishes the superconducting transition temperature of the system.the Josephson current is contributed completely by the s-wave.Using the calculated s-wave energy gap and the corresponding critical temperature we have quantitatively explained the product of Josephson current at 0K and junction resistance, Ic(0)RN ,and the variation of Ic with temperature.In addition,we can explain the observed variation of Ic with bias voltage and the Fraunhofer pattern,and the model is consistent with other SQUID experiments probing the symmetry of order parameter of YBCO.Therefore,the two-component model gives a consistent explanation for the two kinds of experimental results which seem to contradict with each other.We also briefly discuss the experimental method which can distinguish different models.