Superparamagnetic iron oxide nanoparticles (SPIONs) are nanoparticles used in a lot of applications such as batteries, biomedical, … To obtain these nanoparticles, several techniques exist such as coprecipitation, thermal decomposition, sol-gel process but they have some advantages (synthesis in a water media, high crystallinity, high monodispersity) and disadvantages (using organic solvent, large distribution of size, poor crystallinity). The goal of this work is to synthesize SPIONs for biomedical applications (for example as contrast agent for the MRI): SPIONs should be stable in an aqueous media, monodisperse and have good crystallinity and magnetic properties. To achieve this result, microwave process is carried out. However, any study describes the microwave parameter on the synthesis of the nanoparticles. This work offers to determine the best conditions of the microwave to obtain ideal SPIONs for MRI. For this, an experimental design is carried out to determine these parameters thanks to different techniques of characterization (Transmission Electronic Microscopy, Dynamic Light Scattering, X-Ray Diffraction, Thermogravimetric Analysis, magnetic characterizations). With the different results of these characterizations, the best conditions of the microwave are determined, and a simulation of all experiments is realised with a surface response.