The timing accuracy for seismographs directly affects the seismic location ability. At present, seismographs usually use satellite positioning and navigation system for timing service. The time-service module of the seismograph is susceptible to radio frequency interference, which leads to inaccurate punctuality of the seismograph. The main causes of electro-magnetic interference are high-frequency electronic components, power supply modules, circuit design and ground wire deployment. Based on the experiments, it is found that the electromagnetic interference of the seismograph system to the time-service module can be stably reduced by adding an isolation plate, replacing components, optimizing the circuit design and adjusting the arrangement of ground wires. The techniques mentioned in this pater can be used to improve the timing accuracy of the seismograph.