Batch experiments were performed to evaluate the effect of sludge acclimation and contact load on the behavior of phosphorus and organic substrates under anaerobic conditions. Four different sludges were acclimated in the sequencing batch reactors operated by intermittent aeration. All the experiments performed in a bench scale have shown the following results: 1. The unreleaseable phosphorus contents for four different sludges are the range of 16 ㎎ P/g SS to 24 ㎎ P/g SS, depending on the sludge acclimation conditions. 2. All the specific substrate uptake rates(SSUR) are expressed in the first order equation for releaseable phosphorus contents. The reaction rate coefficient, k, has the values of 4.0, 8.9, and 13.8 mg COD/㎎ P/hr, depending on the contact load and sludge species. 3. As reaction proceeds, the ratios of ΔP to - ΔCOD at high contact load are almost constant. in the range of 0.10 to 0.14, but at low contact load, they increase from 0.08 to 0.27.