Abstract: The authors introduce the related theories on silt reinforced with slag powder first.The improvement of silt by adding slag power is attributed to the micro-aggregate filling effect and pozzolana binding effect,and the latter effect consists of hydration,inspiration and ion exchanging.It is suggested that the micro-aggregate filling effect is highly correlated with the fineness of slag powder and the two effects are summed up with framed chart.On the other hand,the tests of unconfined saturated compression,water stability,freezing stability,temperature shrinkage and dry shrinkage of silt consolidated by slag powder and silt consolidated by lime power were conducted and the test results were compared.The results indicate that road performance of silt consolidated by slag powder is better than those of silt consolidated by lime powder,which provides experimental evidence to its engineering application.