There are several disadvantages such as high reagent expenses，serious secondary pollution etc. In the determination of wastewater CODcr using the potassium dichromate method. The non-mercuric method had some advantages which were not only increasing  concentration  of  sulfate that reached to 9 mol/L,but also enhancing the electrode electric  potential of   the oxidizer, potassium dichromate, eliminating the disturbance from Cl-,and decreasing the determination time,having a higher practical value.