1. Physiologically speaking, children's logical thinking ability begins to form at the age of 4-5, and develops slowly before the age of 7. Their understanding of things is only based on intuition and physical feeling, which can not meet the requirements of language learning. At this time, it is often difficult to master the correspondence and spelling rules when learning pinyin.

2. Children in kindergarten don't understand complicated sentences and are eager to learn Pinyin. In fact, it is only from the perspective of mechanical memory to increase their learning burden, which is also a multiplier effect.

3. Children's expressive ability is not strong enough. Many children can't talk fluently in daily life. Pinyin learning is divorced from daily life. Learning Pinyin too early will make it more difficult for children to learn everyday conversations.