Dear Jinkai,
You may export the survey in two ways:
1. From the page that contains the list of Surveys: Click on the survey, then the Export button appears on the bottom of the page, click on it.
it. ![alt text][1]
2. From the survey design page, there is a button on the top-right corner that offer some advanced functionality (among which you have the export function)
![alt text][2]
Then you get an Export dialog where you can choose the format and the language (if more than one) that the survey should be exported on!
![alt text][3]
[1]: http://www.openforis.org/support/upfiles/chrome_2017-07-28_10-22-06.png
[2]: http://www.openforis.org/support/upfiles/chrome_2017-07-28_10-22-41.png
[3]: http://www.openforis.org/support/upfiles/chrome_2017-07-28_10-23-47.png