The invention provides an acid adding machine with an improved acid adding mechanism. The acid adding machine comprises a machine body and an acid adding mechanism, wherein the acid adding mechanism comprises a lifting die head arranged on the machine body and an acid injection head positioned on the lifting die head, the machine body is connected with the lifting die head through a lifting cylinder, the machine body is provided with a guide rod, the lifting die head is sheathed outside the guide rod, and the lifting cylinder drives the lifting die head to ascend and descend on the guide rod. According to the acid adding machine, as the guide rod is arranged, the accuracy in the movement of the lifting die head is relatively high.