AVI video refers to Audio Video Interleave which is a multimedia container format introduced by Microsoft in 1992. To play AVI on iPhone 4 for Mac smoothly, you need to convert video to iPhone 4 MP4 or H.264 first.
For Windows users, please refer to: How to Convert AVI to iPhone 4.
Things you will need:
1. Mac iPhone 4 Video Converter which is a professional AVI to iPhone 4 Converter Mac software.
2. AVI Video files on your Mac computer
3. Your lovely iPhone 4.
Follow the guide, then we will help you figure out how to with play AVI to iPhone 4 on Mac with great quality. First you need to free download this software via link below.
Step 1: Click the "Add" button to import your AVI files to your downloaded program.

Step 2: Click "Format" drop-down list to select an output format for your iPhone 4. And then set a destination folder to save the converted videos. If you are not satisfied with the video effect, you can use the edit functions such as trim, crop, clear the added video files. If you need, you can merge your files into one by clicking "Merge into one file".

Step 3: Click the "Start" button to start convert AVI to iPhone 4 for Mac. Then open iTunes and connect your iPhone 4 to Mac. Add the converted files to iTunes and sync the videos to your iPhone 4.
What is next?
Learn more about Mac iPhone 4 Video Converter:
This AVI to iPhone 4 Converter Mac software can convert various videos (including AVI, WMV, FLV, MOV, MKV, 3GP etc. format videos) to iPhone 4 compatible format on Mac and have the function of editing.
Try to free download now!
Related: Convert DVD to iPhone 4 on Mac, Put Videos to iPhone 4 on Mac