The delay time response function of the waveguide microring resonator is deduced from its optical-field transmission function. The influence of microring waveguide loss on the delay time characteristics is analyzed and the result shows that the microring resonator-based optical delay line applied in the optically controlled phased array antenna system should be at over-coupled condition,which means that the coupling coefficient κ and the microring waveguide loss factor γshould satisfy the relation of κ>(1-γ). According to the criterion of delay time ripple guality factor ε,the method of optimized design of the microring resonator-based optical delay line is established,and the optimized structural parameters of cascaded four microring resonators for target delay time of 0.6 ns,bandwith of 2 GHz,and delay time ripple guality factor less than 1×10-3 ns2 are obtained.