In this study, we pay attention to the formation issue of a discrete-time LTI targeted system by using a sensor network to measure the outputs. Each sensor implements the measurement of partial outputs and this local outputs cannot guarantee the observability of the targeted system. To achieve the formation objective, each sensor is endowed with two-layer dynamics, where one of the first layers of dynamics is a multi-hop decomposition based distributed observer, while the lower layer one is the distributed observer based formation control algorithm. Rigorous analysis shows that under the condition that the system matrix and the output matrix can be collectively detected, the designed observer and controller in this paper can make the sensor observe the target in the set formation and the observed state of each sensor can converge with the real state of the target. Ultimately, the rationality of the theoretical study has been proved by simulation.