This paper designs a time synchronization system with inputs of GPS and IRIG-B time code and very stand crystal and RS232 communication as well as a keyboard,whose hardware uses MCU and CPLD combination structure,where MCU manages communication and display,etc.

The paper introduces the time synchronization conception of the IRIG-B format code and its module construc- tions which include microprocessor,level converter and optically coupled isolator.

This paper explores the power supply, grid and formation of the system in the substation, the actual state of timing, the problems and improving measures.

As for simultaneous time setting of power system automation, suggest that a substation commonly uses a GPS to synchronously create IRIG_B codes to realise simultaneous time setting of all the microprocessor_base protection and automation devices via RS_422/485 ports.

In the method the time interval coupling pair decoupling substitutes the time interval decoupling during the optimizing proce.

According to the principle of the method of pseudorange and SLR time comparison,the computation model of the method of pseudorange and SLR time comparison in the non-rotating geocentric system has been derived in the angle of mathematics and geometry,so it is very important for achieving satellite-ground time synchronization in high precision.

Time transfer by laser is the most precise one in several time comparison methods.