The invention relates to a chemical mechanical grinding device and a grinding pad surface trimming method. The device comprises a grinding table, a temperature control water machine, a sprayer and anadjusting head, wherein the grinding table is used for setting a grinding pad; the temperature control water machine is provided with a water inlet and a water outlet, the water inlet is connected with a deionized water supply device, and the temperature control water machine is used for heating deionized water flowing in from the water inlet to a preset temperature range; the sprayer is arrangedabove the grinding table, is connected with the water outlet of the temperature control water machine and is provided with spray heads, and the spray heads are slantly arranged relative to the grinding pad surface; and the adjusting head is arranged above the grinding table and is used for adjusting and trimming the roughness of the grinding pad surface. The method comprises the steps that a waferafter surface treatment is moved out; the heated deionized water is continuously sprayed to the grinding pad surface through the spray heads of the sprayer to heat the grinding pad surface; and trimming is performed on the grinding pad surface through the adjusting head. According to the chemical mechanical grinding device and the grinding pad surface trimming method, softening is performed on the grinding pad through the heated deionized water, therefore, the contact area between the grinding pad and the wafer is increased.