Analyzed the change rules of the concentration of nitrogen compounds, COD and pH in the upflow ANAMMOX biofilter, and the distribution rules of the ANAMMOX activity and biomass. And furthermore, the relations of the nitrogen compounds concentration to the COD and pH in the ANAMMOX process were studied with the statistical method. The results showed that the dissolved oxygen and nitrogen load together caused the uneven distribution of the ANAMMOX activity and biomass along the filter layer in a "ridge" shape; the existence of heterotrophic denitrification and the consumption of H+ made the COD decrease and the pH increase in the ANAMMOX process; the concentration of the organic matters below 100 mg/L has little influence on ANAMMOX bacteria, and the relations of the substrate NH4(+) -N concentration to the COD and pH showed a good linear correlation. The slopes of the fitting line of the COD-NH4(+) -N and pH-NH4(+) -N were 1.113 8 +/- 0.052 2 and - 0.111 3 +/- 0.001 2 respectively, with the confidence level being 95% and the average correlation coefficient R2 0.982 3 and 0.9850 respectively.