Can i substitute ibuprofen for prednisone?

Depends: Ibuprofen and Prednisone are both anti-inflammatory medications, although Prednisone is significantly stronger. They each have other properties as well. The answer certainly depends on the reason you are taking the prednisone. While not preferred as a long time medication, your prescribing physician should be consulted.

Two different meds: No, even though you might have heard they both have anti inflammatory properties they act through different ways and it is dangerous to try to use one instead of the other for certain conditions. Prednisone can cause significant side effects if not taken properly. Ibuprofen may cause also significant side effects so it is recommended to speak with your pcp before using any of those.