Cell sectorization and improvement of the Chip Energy/Others Interference(Ec/Io) are technologies to offer good quality of services (QoS) and coverage for new and sophisticated power control to achieve high capacity in CDMA cellular mobile communication networks. In this paper, in order to efficient cell sector and to improve the Ec/Io of the pilot channel in CDMA mobile communication systems, I analyze and compare the wide-beam trisector cell(WBTC) with the narrow-beam trisector cell(NBTC) as a method for cell sectorization. The NBTC was compared with the WBTC, using the results of a theoretical analysis, a simulation, a field measurement, in order to examine its effectiveness and validity. As a result, I confirmed that NBTC was efficient cell sector method to minimize interference from adjacent base stations and to increase cell coverage.