In order to study effects of freezing-thawing on characteristics and fractal dimensions of soil microaggregates, samples of brown soil, typical of Northeast China, were collected and subjected to an indoor artificial freezing and thawing test for analysis and determination of composition, mean weight soil surface area (MWSSA), mean weight diameter (MWD) and fractal dimension (D) of soil microaggregates as affected by frequency of freezing and thawing and water content. Results show that changes in these characteristics of soil microaggregates after the treatment varied from fraction to fraction of particle-size. The effect of water content on content of soil microaggregates was significant or extremely significant in all fractions, except the fraction of 0.005～0.001 mm, and so was the effect of the frequency of freezing and thawing. WMSSA first decreased and then increased with increasing freezing-thawing frequency and soil water content. WMD first increased and then decreased with increasing freezing-thawing frequency, but went the other way round with increasing soil water content. And D first decreased and then increased with increasing freezing-thawing frequency, and fluctuated with increasing soil water content. It was found that the treatment first enhanced and then undermined the stability of soil microaggregates and a proper soil water content could improve the stability.