Network slicing enables a single physical network be sliced into multiple virtual networks. Each is customized and optimized according to specific 5G services and business goals. It can accommodate QoS heterogeneity of different 5G vertical services with isolation. In this research, we realize 5G mobile core network slicing based on the NFV (Network Functions Virtualisation) MANO (MANagement and Orchestration) architecture. Our prototype leverages open sources from both OpenStack Tacker and NCTU free5GC to creates 5G core network slicing based on its Network Service Descriptor (NSD). We evaluate and compare the performance between the multiple network slicing system and the one-slice-fits-all single slicing system using three eMBB (enhanced Mobile BroadBand) services of different QoS levels. Our test results show that the former can achieve better throughput and response time than the latter with the tradeoff of increasing its CPU consumption.