In the past 3 years, there is big progress of the foldable display device, so nowadays it has better durability, usability and appearance. As a result, it takes more attraction of customers in the market. In order to persist and expand this trend, we need to develop a water‐drop shape folding hinge to make device which has better appearance, flat and slim. But it has some technical issues such as more folding stress, space occupation, folding trace and so on. We have reviewed those and find optimized design of a water‐drop shape folding hinge. We have made device mock‐ups and evaluated its performance. It could be taken more attraction of customers in the market.