Low-density cobalt-phthalocyanine (Co-Pc)/Fe nanocomposite particale with both adjustable electric and magnetic properties were synthesized using one-step thermolysis. The nanocomposite particales wrer fully characterized by fourier transform infrared spectroscopy, X-ray diffraction analysis, scanning electron The magnetic hysteresis loop and microwave electromagnetic parameters of the nanocomposite particles were measured. The magenetorheologyical (MR) properties of the MRsuspensions based on the nanoncomposte particaled dispersed in methyl silicone oil were investiated as functions of weigth percent of particles, nanocomposite consisted of micrometer-sized regular spheroids with hundreds of thousands of Co-Pc-coated α-Fe nanoparticles on the inside and Co-Pc layers on the surface of the spheroids. It showed good characteristics of antioxidation and high magnetic susceptibility. For nanocomposites containing 82.7wt% Fe, woth omcreasomg, ocrpwave freqiemcu. the complex permeability (Ur) occurred. In comparison with conventional carbonyl iron powders, the density of the nanocomposite particles was much lower, and εrdecreased signiflaantly while μr hardly changed. magnetic field induced shear stress of the MR suspension based on nanocomposites with 89.7wt% Fe was basically independent of T and γ but increased abruptly with increasing H. With increasing T. response time of the MR suspension to an external masgnetic field seemed to decrease. The results suggested that the synthesized Co-Pc/Fe nanocomposite particles with different compositions could be utilized as an excellent microwave absorber and as dispersed particles of high-performance MR suspensions.