//方法一

NSString *appDomain = [[NSBundlemainBundle] bundleIdentifier];[[NSUserDefaults standardUserDefaults] removePersistentDomainForName:appDomain];

//方法二

- (void)resetDefaults {

NSUserDefaults * defs = [NSUserDefaultsstandardUserDefaults];

    NSDictionary * dict = [defs dictionaryRepresentation];

for (id key in dict) {

        [defs removeObjectForKey:key];

    }

    [defs synchronize];

}