How can I start import export business but I don't money to invest?

You shall know:

1- Who is your customer

2- where is your market

3- What products you are  familiar with to export or import

I doubt you can start without any money especially for the 1st time but if you can get a Purchase Order from your client with down payment that can cover at least your dry cost (it covers the cost of the goods, shipping and logestics to your client)

Ex. your customer is looking for special screens and he can pay 0nly %50 as down payment and the remaining after the delivery then you need to make sure that you can find the screens prices including shipping and delivery cost less than or equal to the %50 down payment.

You have to have great skills in nogetiation with suppliers to get Good discount with payment terms and conditions that work with you.

from other side you need to discuss with your customer to get more down payment if possible .

Two ways 

1. Explain your trade ideas to a local khafeel and get a commercial trade license through him.

2.  Get a business loan / Investment from bank or finance investors 

Excellent answer given by Mr. Mohamed Basem. I'd like to also suggest that you find an investor whom you trust and who trusts you and partner with him in this business. You'll do the work required and he'll pay the capital and you can both share the profit. If you pay no share at all in the required capital and your partner pays 100% you can go for an 70-30 share where he gets 70% and you get 30%.