With the word physical fitness getting more and more attention in our country, physical fitness has been widely developed in our country. Therefore, in recent years, the students' physique has received attention from all aspects of society, and improving the students' physique has also become a new topic for physical education workers. I try to discuss the effect of physical fitness training on children's cognitive ability from the perspective of physical fitness training. To provide theoretical basis and reference for intervention of children's cognitive ability training methods. So as to promote the improvement of children's cognitive ability and provide guarantee. This paper studies the influence of physical fitness training on children's cognitive ability by using the methods of literature, observation and experiment. The following conclusions are drawn: 1. Before the experiment, 8 children from Qinhuangdao Aikushao Physical Fitness Center were tested for attention cognitive ability and memory cognitive ability. Among them, 8 children were deficient in cognitive ability to varying degrees. Compared before and after the experiment, physical fitness training has an effect on children's attention cognitive ability.3. Compared before and after the experiment, physical fitness training has an effect on the improvement of children's memory cognitive ability.