Can we visit Great Wall of China from Kunming?

You are advised to take a flight to Beijing, which houses the most famous GW sections of CN. I personally recommended you visit Badaling. Upon landing at the airport, you are suggested to take shuttle bus line 2 to Xizhimen. Alighting from the bus and you will see North Railway Station right away. You may take train S2 from the train station to the Wall in around 1h.
Hope you enjoy your time there!