To meet the requirements for miniaturization, broadbandization, integration, and Electro Magnetic Compatibility(EMC) in radar and communication systems，the ceramic nesting technology was used to design and fabricate a low-loss X-band Surface Mount Technology (SMT) microstrip circulator based on Mg ferrite materials. Through three-dimensional full electromagnetic simulation, a microstrip gyro-magnetic junction with comb structure was designed to achieve device miniaturization and broadbandization. To realize SMT packaging, a ceramic-filled metallized via structure was optimally designed using HFSS, and the St12 metal with high permeability was used as a shielding cover to ensure that the circulator can work independently without interference from other components in the system, achieving electromagnetic shielding and magnetic conduction. Finally, the device was fabricated and tested according to the optimal design results. The test results demonstrated that the designed SMT circulator had a full package size of 6 mm×6 mm×4 mm, with a bandwidth of 60%, Loss<0.8 dB, Isolation>18 dB, and VSWR<1.30. The resulting circulator shows no electromagnetic interference with the outside world, and is suitable for large-scale automatic mounting.