If I win the lotto can I collect the money even though I'm on ssi?

yes.  but you will lose the SSI.  SSI is welfare.  if you get money (from lottery or otherwise), and if it is "too much" (generally $2,000 - 3,000 or more), then you are no longer eligible for SSI unless and until the money is gone (or below the maximum amount allowed)

If you are on Supplemental Security Income (SSI) you are required to report any change in circumstance to the Social Security Administration (SSA).  Follow this link for information about your local SSA office. Your winnings may make you ineligible for that month, or a few months, but you can enjoy the independence.  Once your asset level reaches SSI eligibility again, notify SSA.  In some circumstances, you may not lose benefits if you use the winnings in the same month.