A polarographic method for determination of molybdenum in soil was developed. In supporting electrolytic solution of sulphuric acid, sodium chlorate and amygdalic acid, a catalytic wave of molybdenum can be formed with a detection limit below 1 ppb. Since 1975, large amount of soil samples have been analyzed and it is proved satisfactory. For determination of available molybdenum in calcareous soils 5g of soil sample is extracted with 50 ml of ammonium oxalate and oxalic acid solution (pH 3.3),shake for 8 hours as conventional way. Transfer 10 ml of the extract into a small beaker (GG-17 glass) Evaporate to dryness. Ignite to destroy oxalate. Dissolve the residue with 2.5 ml of 2N sulphuric acid and 2.5 ml of 0.4M amygdalic acid, and then add 5.0 ml of 50% sodium chlorate, and mix evenly. Record the polarogtaphic wave from -0.1V. Removal of oxygen is unnecessary.