In sensor networks Target Tracking defines how accurate a targets position can be measured. We consider both stationary target and mobile target. Since the mobile target is unknown, the mobile sensor controller utilizes the measurement collected by a wireless sensor network in terms of the mobile target signal’s time of arrival (TOA).We proposed time of arrival2 (TOA2) algorithms which consider time to live (TTL). We investigate the correlations and sensitivity from a set of system parameters. We derive the minimum number of mobile sensors that are required to maintain the resolution for target tracking in a mobile sensor network (MSN).The simulation results demonstrate the tracking performance can be improved by an order of magnitude with the same number of sensors when compared with that of the static sensor environment.