For samples with strong toughness and thermal sensitivity that are difficult to grind at room temperature, such as rubber, plastic, food, minerals, animal and plant tissue samples, pharmaceuticals, samples for biochemical DNA detection and cell disruption. The samples are cooled in liquid nitrogen (-196 ℃) and pulverised with a magnetically driven impactor. The samples become brittle and the volatile components are preserved under the low temperature, so that a good grinding effect can be achieved.