Step one:
Draw an arc first.
Step 2:
Draw two vertical lines above the arc.
Step 3:
Draw two more downward-curving arcs on top, paying attention to drawing two layers.
Step 4:
Then draw more drooping arcs below the two arcs to form the willow branches.
Step 5:
Use the same method to draw some curved branches on it.
Step 6:
Then draw some small ovals on the arc as willow leaves.
Step 7:
You can also use small short lines to add a little texture to the willow tree.
Step 8:
Finally, paint it with a nice color, and the willow tree is finished.