The purpose of the phase 1 study is to assess the safety and pharmacokinetics of PEG somatropin, which administered once per week, compared with the daily used somatropin, and to evaluate the safety and possibility to replace daily used somatropin.

Inclusion Criteria:

• have a height less than two standard deviations (SD) below the median height for individuals of the same age or height, a growth velocity (GV) ≤4 cm/yr, a GH peak concentration <7 ng/ml in two different provocative tests, a bone age (BA; ≤9 years in girls and ≤10 years in boys) at least 2 years less than his/her chronological age (CA);be in preadolescence (Tanner stage 1) and have a CA >3 years;have a height value recorded 3 months before the start of GH treatment to calculate pre-treatment GV; receive no prior GH treatment or stop the GH treatment for more than 4 weeks;sign informed consent

Exclusion Criteria:

• Patients with Liver and kidney dysfunction (ALT> upper limit of normal 2 times, Cr> upper limit of normal), hepatitis B virus detection, antigen-HBc, HBsAg and HBeAg are positive
• patients with known to a highly allergic constitution or allergic to the drug of this study
• Patients with diabetes, serious cardiopulmonary, blood system, malignant tumor and other diseases or systemic infection in immunocompromised and mental diseases
• Patients with other growth disorders, such as Turner syndrome, constitutional delay of growth and puberty, Laron syndrome, GH receptor deficiency, girls with growth delay have not ruled out chromosomal abnormalities
• Participated in clinical trials of other drugs in 3 months
• Other cases that the researchers considered unsuitable for this clinical trial