Officers from West Midlands Police executed a drugs warrant at the unit in Droicon Industrial estate in Portway Road, Rowley Regis, at around 2.30pm on Thursday.
A spokesperson said: "We recovered 812 plants, which will now be destroyed, and dismantled thousands of pounds worth of growing equipment to ensure it can't be used again.
"Cannabis farms are very dangerous places and pose a serious risk of fire, with the electricity meter often being bypassed and the circuits seriously overloaded.
"No one was arrested yesterday but we know that sometimes the people working in the ‘farms’ are victims of human trafficking and working against their will.
"Every cannabis farm we destroy helps prevent a vicious circle. The plants won’t end up as street deals, the profits won’t go on to fund other crime, and they won’t ruin lives or pollute our communities."
Residents with suspicions about a premises being used to grow cannabis should visit www.west-midlands.police.uk/your-options/cannabis-factories.