Abstract: Some of the effective urease inhibitors, such as N-(n-butyl) thiophosphoric triamide(nBPT) and phenylphosphorodlamidate(PPD), as well as hydroquinone(Hg),have recieved considerable attention during the past decade. The transcformation of urea-N in soils is influenced by the addition of urease inhibitors. which can retard the hydrolysis of urea, thus reducing the losses of urea-N as NH3. However. The effectiveness of the inhibitors is dependent on environmental conditions, such as soil pH, aeration, and the residue amended. In recent studies urease inhibitors have shown promise under conditions which are conductive to substantial NH3 loss and which are favourable for the inhibitor's action. Inhibitors may therefore provide an alternative to high rates of urea, ensuring a optimum yield, a safe environment and a practical farming technique for sustainable agricultural production. In this review,comparison of the urease inhibitors in their effects on urea-N trasformation, N uptake by crops and crop yields is made to help us have a better understanding and consideration of potential values, acting conditions and effective rates of urease inhibitors for farming practices.