That is assuming you put them together as adults.

The frog will be extremely tempted to go after the axolotls gills (the frilly extensions on the side of their head). This will be quite painful and could lead to infection.
The axolotl has ridges on the inside of it's mouth at the gum line which are used to grab and tear. This could severely injure the frog and frog's do not have the regenerative capabilities that axolotls do. Bear in mind that the older the axolotl gets, the slower they regenerate.

I have kept and bred both species and I would not house them together. Axolotls also should be housed at cooler temperatures than the frogs.