Unity natively imports Maya files. To get started, simply place your .mb or .ma file in your project’s Assets folder. When you switch back into Unity, the scene is imported automatically and will show up in the Project view.
To see your model in Unity, simply drag it from the Project View into the Scene View or Hierarchy View.
If you are using IK to animate characters you have to select the imported .mb file in Project View and choose Bake IK & Simulation in the Import Settings dialog in the Inspector.
In order to import Maya .mb and .ma files, you need to have Maya installed on the machine you are using Unity to import the .mb/.ma file. Maya 8.0 and up is supported.
If you don’t have Maya installed on your machine but want to import a Maya file from another machine, you can export to fbx format, which Unity imports natively. Install the latest version of FBX for best results. For general export guidelines see HOWTO_exportFBX.
Once exported Place the fbx file in the Unity project folder. Unity will now automatically import the fbx file. Check the FBX import setting in the inspector as mentioned in HOWTO_exportFBX
When Unity imports a Maya file it will launch Maya in the background. Unity then communicates with Maya to convert the .mb file into a format Unity can read. The first time you import a Maya file in Unity, Maya has to launch in a command line process, this can take around 20 seconds, but subsequent imports will be very quick.