There's a couple ways you can try to handle this. The bottom line, though, is that ebooks are reflowable content, unlike a print book or a PDF for instance, so you only have so much control over how the content actually appears.
Take a look at the this page, which describes the
page-break-inside CSS property. If you set this to
avoid for your list, it instructs the reader that it should try not to break this element across multiple pages, or in other words, it will try to keep it all on one page. The downside of course is that you may end up with a large vertical whitespace before the content if the reader decides it needs to move the entire thing onto the next page in order to fit it.
This can also potentially cause problems if your content really is too big for a page (which, remember, you don't know the size of for an ebook). Depending on the reader, it might break the content onto multiple pages if it has to (ideally it will do this), or it might truncate whatever content doesn't fit (which would suck).
You might also look at the
page-break-after which can help make things look better if they are moved entirely onto a different page.
Another option is to try to reformat your list. For instance, I had a long list which I replaced with a table here in order to make it a "double-wide" list, so that it would only require about half as much vertical space, and more easily fit onto one page. In another instance (here), I turned the list sideways (also with a table) so that it would fit better.