Magnetic tunnel junctions (MTJs) with different sizes from 5μm×5μm to 15μm×60μm were fabricated on 4_inch Si/SiO_2 substrates. Their mag netoelectronic properties were investigated using the four_probe measuring system. The typical values of junction resistance_area product and tunneling mag netoresistance (TMR) ratio of the MTJs are 16 kΩμm^2and 18% respectively. The absolut eerrors of junction resistance_area product and TMR ratio are within 10% and 7% respectively for all the MTJs. All of the MTJs fabricated and measured show a good uniformity. Our experimental results show that such MTJs can be used to fabrica te the prototype demonstration devices for magnetoresistive random access memory .