The purpose of this study is to establish a new Chinese children's speech and language norm by obtaining the latest data of speech and language development of children aged 2 ~ 6 from different regions in China. At the same time, the overall development level and group differences of speech and language in Chinese children aged 2 to 6 years, and the influencing factors of speech and language development in Chinese children aged 2 to 6 years were also discussed.

1. To establish the norm of speech and language development in Chinese children aged 2 to 6 1063 normally developing children and 96 abnormally developing children will be retrospectively enrolled from the medical records of stratified, randomly selected centers. A total of 4137 children with normal development and 448 children with abnormal development aged from 2 to 6 years old will be selected from 11 hospitals in China by multi-center, stratified, unequal proportion random sampling and face-to-face survey. Children's speech and language development was assessed by the Speech and Language Development Scale for children aged 2 to 6, compiled by the Linguistics and Language Research Centre of the Education University of Hong Kong.
2. To investigate and analyze the present situation of speech and language development of children aged 2-6 in China The present situation of children's speech and language development was analyzed, and the differences of gender, age, birth and other influencing factors were statistically analyzed.

Inclusion Criteria:

For normally developing children

1. All children must meet all of the following criteria simultaneously:

2. Informed consent of legal guardian or group representative;

3. Age from 2 to 6 years old, male and female;

4. Native speaker of Mandarin;

5. Children in kindergartens and hospitals are professionally assessed as normal development, which is defined as children without intellectual development disorder, developmental speech or language disorder, autism spectrum disorder, and attention deficit hyperactivity disorder.

   For abnormally developed children

6. Informed consent of legal guardian or group representative;

7. Age from 2 to 6 years old, male and female;

8. Native speaker of Mandarin;

9. Children with intellectual development disorder, autism spectrum disorder and attention deficit hyperactivity disorder are assessed professionally in the hospital; Diagnostic criteria were referred to Diagnostic and Statistical Manual of Mental Disorders (DSM-5)

Exclusion Criteria:

For normally developing children

1. Poor coordination;

2. Other unsuitable children considered by researchers, such as children whose developmental level is basically normal but whose environmental and socio-economic factors (premature birth, low birth weight, malnutrition, abuse, etc.) have been verified to affect language development.

   For abnormally developed children

3. Study the poor fit degree;

4. Have visual and hearing impairment;

5. Other unsuitable children considered by researchers, such as children with other organic dysfunction, such as cerebral palsy, congenital genetic diseases, epilepsy, etc.

2 to 6 years of normal and abnormal development of children in 11 hospitals in China (covering central, east, South, west, North and east China) North area) and the corresponding area of the kindergarten