Thank you Daixiwen for your help.
I found how to solve my problem. It was my first time I had to use NIOS IDE. Solution was quite simple...
Kiamur, I don't know if it is going to help you. For my case, I have 2 components in my SOPC design " on_chip memory" and "rambootloader". When I create my project on NIOS IDE, I specify the .ptf of the NIOS architecture made with SOPC. Then, when I build my project, it automaticcaly creates the rambootloader.hex and onchip_memory.hex for my components ( the name.hex depends of the module name of your components in SOPC). It is also important that your C code fits with the design from SOPC: base adresses and IRQ. Finaly, you can generate the NIOS with SOPC, then compile in Quartus.
Daixiwen do you have an idea if it is possible to re-compile the NIOS part in Quartus after each modification and not the full design to earn time?
Regards,