The method includes steps: (1) calculating and storing degree of interference between each scrambling code group in all scrambling code groups and other each scrambling code group; the degree of interference indicates degree of crosscorrelation between two scrambling code groups; (2) finding out assignment of sector scrambling code group with minimal
total degree of interference in TD-SCDMA
system; (3) based on
coincidence relation between scrambling code group and down going
pilot frequency code, through assigned scrambling code group for each sector, determining down going
pilot frequency code for own sector, and selecting a scrambling code for own sector. Considering disturbed condition caused from relativity between composite codes, the invention raises interference killing feature of
system and lowers influence on capacity of TD-SCDMA
system from interference between codes in same frequency in network.