On the basis of considering each factor of urban public traffic line network,  the decision-making method for the optimization of urban public traffic line network is set up by grey theory and fuzzy theory.  This paper proposes to use interval numbers of three parameters to present grey fuzzy numbers.  A comprehensive optimization method for urban public traffic line network is given by using theories above.  It was applied to the practical optimization of urban public traffic line network in the city.  Applied results indicate that the method improves the efficiency of urban public traffic line network.