Results The online derivation technicque overcame the deviation arised from manual operating and serial detecting technicque could enhance both reliability and accuracy of determination.

The dioptric method was adopted in this paper for quick and high accuracy determination of lactose content in milk against that of low accuracy and complicated operating in domestic milk industry.

The method is able to decrease the loss of se in sample decomposition, shorten the time of complexing and extraction and raise accuracy of the determination of se.