This paper deals mainly with method of elimination of interference of iron and oxelate by nitric acid-perchloric acid for polarographic determination of available moly-bdenum in soil. The procedure is described briefly as follows:2g of soil sample is extracted with 20 ml of ammonium ozalate and oxalic acid solution (pH 3.3),shake for 8 hours as conventional way (or shake for 30 minutes and allow it to stand over night).Transfer 1 ml of the extract into a 25 ml beaker. Evaporate to dryness. Add 10 drops of nitrie acid (0.05 ml per drop) and 2 drops of perchloric acid. Evaporate to dryness at higher temperature. Cool and (1:1). Evaporate just to dryness, dissolve the residue with 5 drops of hydrochloric acid cool and dissolve the residue with 1 ml of 2.5 M sulpnuric acid and 1 ml of 0.5 M phenylhydroxyacetic acid, and then add 8 ml of saturated solution of potassium chlorate, and miz evenly. Measure the peak height with JP 1 A polarobraph. The prucodnrc is very simple and rapid with satisfactory accuracy and precision. The method can be used for direct determination of available molybdenum in acid, neutral, and alkaline soils without separating iron.