Try 'Corner Radius' in the properties of the rectangle.

HI only Pro edition support this feature

There is a way to create rectangles with rounded corners on any layer in **EasyEDA Std** but it is a bit clunky. 1. First open a new PCB. This is the **Source** PCB; 2. Use the **Set Board Outline...** Tool to create a rectangle with rounded corners; 3. Select the whole of the newly created Board Outline and change it whichever other layer it is required to be on; 4. Copy or cut and paste it to the desired **Destination** PCB or Footprint. * Note that creating a second Board Outline using the Set Board Outline Tool in the Source PCB will overwrite any existing Board Outline. * Note also that it is not possible to use this technique to create rounded rectangular shapes in the Schematic.