Abstarct: In this research bismuth ferrite nano-particles (BiFeO3) were synthesized using sol-gel method. In the first, the effects of drying temperatures of synthesized solution at 80, 100, 120 and 150 ℃ on the structural, optical, dielectric and magnetic properties of the fabricated nano particles were investigated. XRD and dielectric analyses show the sample dried at 120 ℃ have the most pure BFO phase less dielectric constant variation with increasing frequency from 20 to 10000 KHz. FESEM images shows average grain size increases with increasing the drying temperature. Magnetic analysis indicates that all samples shows saturated magnetic hysteresis loops and the sample dried at 150 ℃ have much larger saturation magnetization compared to others which can be due to the presence of the magnetic secondary phases in this sample. To modify the synthesize condition in order to decrease the impurity content, the drying temperature 120 ℃ was chosen and the effect of annealing temperatures on structural, morphology, dielectric and magnetic properties of the BiFeO3 nano-particles were investigated. XRD analysis revealed that the sample annealed at 800 ℃ with about 1 percent secondary phase has the most purity content. FESEM images revealed that average grain size increases with increasing the annealing temperature and the sample annealed at 800 ℃ has the largest grain size. Magnetic hysteresis loops measurements show the samples annealed at 500 ℃ to 700 ℃ present saturated magnetization while the sample annealed at 800℃ shows a linear increase in magnetization with increasing the applied magnetic field. This linear behavior is due to the larger grain size, larger than the spiral spin structure’s period, in this sample which shows bulk bismuth ferrite magnetic behavior. In order to improve the magnetic property of the nanoparticles, the effects of Ni and Mg doping in Fe site of BiFeO3 were examined. Drying temperature of 120℃ and annealing temperature 800℃ for 4 hours were chosen as a synthesis conditions. XRD results shows introducing Ni and Mg at Fe sites increase the impurity content in comparison with the un-doped sample. Dielectric constant measurements indicate increasing the dielectric constant of the samples with doping. Investigation of the magnetic properties of the samples shows that substituting Ni+2 and Mg+2 at Fe+3 sites increase the ferromagnetic properties of the BFO which could be due to the difference of the magnetic moments of the substituted ion’s with the Fe+3 ion or presence of the secondary phases in the doped samples.