The invention provides a method for improving the density of compounded cement slurry. The method comprises the following step: adding a weighting agent into the compounded cement slurry to improve the density of the compounded cement slurry, wherein the weighting agent comprises titanium oxide and/or manganese oxide. According to the method provided by the invention, the specifically selected weighting agent is added into the compounded cement slurry so that the density and compression strength of the compounded cement slurry are improved; the method is simple, convenient to operate and easyto popularize in a large scale; the problem that the density of the cement slurry is improper and needs to be calculated and compounded again, caused by the fact that pressure in a well is changed ina well cementation process, is solved, so that the well cementation efficiency and quality are improved.