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.