The invention discloses an ore selecting method for lowering the content of magnesium oxide in Nelson reselection precious metal concentrates. The ore selecting method comprises the following steps that the Nelson reselection precious metal concentrates are ground into minus 0.074 mm by 60%-75% through a ball grinder, copper sulfate is added in the ore grinding process, and the adding amount of the copper sulfate is 80-100g per ton of the Nelson reselection precious metal concentrates; and flotation reagents are added into the Nelson reselection precious metal concentrates after ore grinding,the flotation concentration is controlled to be 28%-35%, rapid flotation is conducted on ore pulp under the condition of high-rotation-speed stirring, and concentrates with the content of the magnesium oxide lower than or equal to 6.6% can be obtained after flotation. By means of the ore selecting method for lowering the content of the magnesium oxide in the Nelson reselection precious metal concentrates, valuable metal is recycled by conducting ore grinding and flotation technologies on the Nelson reselection precious metal concentrates, the recycling rate of the precious metal is greatly increased, the recycling rate of gold and the recycling rate of platinum can reach 97%-99% and 91%-99% correspondingly, about 90% of the magnesium oxide can be removed, and the content of the magnesium oxide in the Nelson reselection precious metal concentrates can be lowered within 6.6%. According to the ore selecting method for lowering the content of the magnesium oxide in the Nelson reselection precious metal concentrates, devices involved in the whole process are few, the technological process is simple, the processing cost is greatly reduced, and industrial production on the spot is easy toimplement.