Rotary cranes are widely used to transport heavy loads and hazardous materials in various environments, such as shipyards, factories, nuclear installations, and construction sites. Because horizontal motion of booms in rotary cranes typically generates undesirable two dimensional load sway, a trajectory generation method is proposed for achieving boom positioning and residual load sway suppression. Firstly, a partial linearized dynamic model of a rotary crane that includes a centrifugal force term responsible for two dimensional load sway is derived. Next, an S-shaped curve trajectory that can suppress residual load sway is generated by numerical calculation. The parameters of the trajectory can be obtained only by solving algebraic equations. This trajectory may be applied to conventional industrial controllers for reducing their system construction cost. Finally, comparative simulations and experimental results demonstrate the effectiveness of the proposed method. Therefore, the crane can be precisely operated without sensor systems for measuring load sway, consequently, the structure of the crane can be simplified and implementation cost can be reduced.