The Co 0.3 Zn 0.7 Fe 2 O 4 nanocrystalline synthesized by the Co-precipitation method with two techniques based on different in initial molar concentration (pH suspension).The structural and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), High Resolution -Transmission Electron Microscope (HR-TEM), Fourier Transform Infrared (FTIR) and vibrating sample magnetometer (VSM). The results suggest the grain size for first technique in the range of 6.14:13 nm and second technique in the range of 8.8:24.4 nm as the calcination temperature increases from 100 to 600°C respectively with different in initial molar concentration (pH suspension) for all techniques. X-ray analysis showed that the samples were cubic spinel structural ( kind of inverse spinel oxide). The crystallinity is improved with the increases calcination temperature for all techniques and that proved by the FT-IR and XRD results and compound purity fabricated. HR-TEM analysis showed that nanoparticles size and the shape based on the initial molar concentration (pH suspension) and the calcination temperatures and also indicates that degree of agglomeration for all samples. VSM analysis showed that all the coercivity values were low enough to emphasize that the ferrite was a soft ferrite or super-paramagnetic behavior for most samples.