How can I fix my big front teeth without braces?

Without seeing any photographs it's very difficult to comment on the best option for you. But Invisalign is a good treatment option in case you don't want to wear braces and you want to correct your front teeth. 
Should you have any more questions or want to share photographs it will be easier for me to give you more accurate treatment options. 
Regards 

I'd really like to answer your question with more accuracy but since I don't have a photo, I can give you some general suggestions. The simple answer is to get veneers. It would probably take at least 4 veneers to fix the tooth sizes. The 2 teeth on either side need to be made larger while the ones in the center need to be made to look smaller.  (The foregoing might also be able to be done with dental bonding.) Another alternative could be to do the clear braces like Invisalign. I hope this helps. The best idea is to find an experienced cosmetic dentist to evaluate your situation.