Ecological filter was constructed to remedy Northern water in landscaping function. Nitrogen transition and its course in different recycling rate were studied by controlling the period. The action mechanism of landscaping water treated by compound substrate was analyzed deeply. Data showed that DO was improved from 7 to 11 and kept high when the recycling period was 1 hours and 1.5 hours. C/N was improved from 4-6 to 6-10. Removal ratios of NH4+ -N, NO2- -N and TN increased with recycling rate improving. Transition coefficients of NH4+ -N and NO2- -N were 0.885 3 and 0.968 5 under 1 hours and 1.5 hours period. The highest coefficient of NH4+ -N and NO2- -N was 0.942 4. Improving of recycling rate made the nitrification more rapidly and completely, and the transition approach of nitrogen was shortened. More rapid the recycling rate was, more direct was the transition.