A use of low-thrust propulsion systems such as ion engines becomes popular in deep space missions because of their high Isp. In order to design low-thrust trajectories simply, this paper proposes a new shape-based strategy using angular momentum. In this strategy, trajectory designing space is not position space but angular momentum-state of the spacecraft space. Using this designing space, it becomes possible to keep simplicity of the shape-based strategy if a shape of the trajectory is complicated. In this paper, as a demonstration, circular-circular transfer trajectories and elliptic-to-elliptic transfer trajectories are designed. Moreover by defining new rotational coordinates - alternating rotational coordinates, it becomes possible to describe low-thrust trajectories as simply shapes.