3. Random method: In commercially available formula subgroup and Friso formula subgroup, infants will be included randomly. Random allocation sequence is generated in six trial centers by the editorial department of Chinese Journal of Evidence-Based Pediatrics, included infants are chosen and their information including name, gender, their parents' name and telephone is reported to the editorial department of Chinese Journal of Evidence-Based Pediatrics via WeChat. Then group division information is acquired, the tested commercially available formula and Friso formula are given out to infants accordingly.