Sharepoint - Delete all survey responses

• Open site manager by adding *_layouts/sitemanager.aspx* in the url. (e.g) http://www.servername:10001/_layouts/sitemanager.aspx
• You can access the same in Site Actions >> Manage Content and Structure ( in SP 2007) (or) Site Settings>> Site Administration>> Content and Structure (in SP 2010).
• Navigate down to your survey.
• Select all responses and go to Actions >> delete.

Alternatively, you can find a useful link here

While there are ways to delete all items from a list (e.g. through powershell on the sharepoint server) (I would advise testing this code on another list or dev environment first to make sure you understand what it is doing):

$web = Get-SPWeb http://mysite
$list = $web.Lists["My Survey"]

while($list.Items.Count -gt 0){$list.Items.Delete(0)}

Another simple option is to save the list as a list template (without the content), then create a new survey list from the site template:

Click List Settings -> Save List as Template. Make sure "Include Content" is unchecked. Click OK. Go to Site Actions -> Create List. Find the list template you created and click OK. Give it a new name (e.g. People survey 2013). Now you have a copied empty survey list with the original data in tact as well. :)