Moisture is one of the prime factors causing oil-impregnated bushing insulation degradation, it is of great significance to research the influence of moisture on condenser bushing"s dielectric property based on HN dielectric relaxation model. Five 72.5KV bushing samples with different initial moisture contents are prepared, then FDS of them is carried out, and HN dielectric relaxation model were applied to fitting curves of FDS. The influences of moisture content on parameters of HN dielectric relaxation model were analyzed. The results show that moisture content has a significant effect on the relaxation time constant t, the relaxation intensity Δe and shape parameter b; with the increase of moisture content, the relaxation time constant t decreased, the relaxation intensity Δe and shape parameter b increased with the rising of moisture content; the relationship between moisture content and t, Δe, b satisfy the log-linear, exponential, linear relationship.