Our objective is to determine the content of protein and of lactose in milk and whey with a new innovative method easy to implement and fast, which is based on the coupling of membrane ultrafiltration operations with electrical conductivity measurements and measures the severity of the Dry Extract (DE). The proteins and lactose determined by the innovative new method was compared with the official method for ten samples. The innovative method gives the results accurate and very close to those obtained by the official method for products of milk and whey. Compared to the official method, the values obtained by this method have a difference about 2% of protein and 1% of lactose.