In this paper, power allocation and target assignment is considered as a promising way to obtain low probability of interception (LPI) in the radar network. Spatial diversity in the netted radars gives us a flexibility to control power intelligently and radar assignment dynamically in such a way that not only detection performances satisfied but LPI characteristics of the network are optimized. We formulate this problem as a non-convex and nonlinear optimization problem associated with detection performance constraints. The optimum solution of general problem is complicated and cannot be solved mathematically. We relaxed problem to more tractable form for the networks with low complexity in which combination of radar's information cannot be handled. In the considered scenario, for each target only one radar is assigned and each assigned radar can only transmit one target's information. We propose a simple framework to obtain optimum power allocation and radar assignment strategy due to spatial diversity of netted radars. The framework has lower complexity compared with optimum exhaustive search algorithm and simulation results show effectiveness of proposed algorithm in satisfaction of detection performances and improvement of LPI specification of radar network.