The defect effect in the two_dimensional (2D) negative permeability material, co nsisting of copper hexagon split ring resonators (SRRs), is investigated. The pr inted circuit boards with SRRs on one side are fabricated using a shadow mask/et ching technique. We use a rectangular waveguide system to measure the X_band tra nsmission in 2D negative permeability materials with different dot and line defe cts. The measured data shows that there is only one resonance frequency and high quality factor \%Q\% for a 2D negative permeability material without defects. T he main resonance frequency has a shift and the resonant peak value decreases wh en the defect SRRs are introduced into the samples. We consider that the defect SRRs break the periodic structure of the samples, which results in the shift of the main resonance frequency and the resonant intensity. The investigation of th e defect effects is important not only for the understanding of the characterisf ics of the negative permeability material, but also for the realization of the l eft_handed metamaterials in the infrared and visible region.