Planar filter has become one of research topic that grows rapidly nowadays, considering the vast utilization, mainly for telecommunication application. This article presents the optimization process of microstrip filter at 600 MHz frequency by utilizing the ring-square structure. This structure is chosen as it may provide high quality factor (Q-factor). Measurement result shows that the optimized result inherits high Q-factor, marked by the narrow bandwidth, of about 3.3%. The obtained filter is also having low return loss down to -30.665 dB, and low insertion loss, of about -6.849 dB. Therefore, this filter is suitable to be applied on telecommunication system component, mainly that require sub-component with planar geometry.