A rapid UV-Vis spectrophotometric method was proposed to determine the concentration of DMP in aqueous solutions. The linear concentration range of DMP solution at the range of 250～400 nm is 05～70 mmol·L-1. At 275 nm, the linear fitting equation is A=0030 7c+0133 0 with a correlation of 0980 9. The detection limitation is 946×10-5 mmol·L-1, the RSD (n=6) of the method were at the range of 0100%～0612%. The recovery ratio for salt solutions sample is 95%～104%. Temperature, pH, and coexisting K+, Na+, Mg2+, Cl-, Br-, I-, SO2-4 ions do not affect the detection. The coexisting CO2-3 and HCO-3 ions can be eliminated with acidification. The results showed that the proposed method is simple in pretreatment process and has high accuracy and precision. It is a quick measurement method of DMP concentration in water solution, and can be used to measure DMP concentration in reverse flotation tail liquid and reverse flotation material pulp.