This paper investigates the nonuniform line coverage control problems for a group of unmanned vehicles in unknown environment. The objective of nonuniform line coverage control is to deploy the vehicles to the optimal locations, such that the regions with higher density can get more attention from the vehicles. For the unknown distribution of interested information (density function), a spatial estimation algorithm is presented to approximate the density function. Then, based on the estimated density function, a distributed line coverage control scheme is proposed such that the vehicles can converge to the optimal deployment. The stability and feasibility of the proposed coverage control system are strictly analyzed. Finally, numerical simulations in PLEXE are performed to verify the effectiveness of the proposed approaches.