In the paper, a linear extended state observer (LESO) is designed for ship heading control with wave disturbance via linear active disturbance rejection control (LADRC). In frequency domain, the tracking ability and disturbance rejection capability of LESO has been analyzed in details. Furthermore, the tradeoff between the closed-loop stability and the system requirements, i.e., rudder, input actuator, can be achieved via parameter tuning, together with active disturbance filtering. Ship heading control is used to as a case study to prove the efficacy of the proposed LESO with simulation experiments.