Objective To explore the expression of naturally occurring plasma anti-? amyloid (A?) antibody in children and youngsters .Methods According to each 10 years, 28 healthy cases aged from 1~30 years old were diviedd to 3 groups.In the 3 groups,the plasma anti-A? antibody was detacted by immunostained with paraffin sections from Tg2576 mice brain to make a specific tissue amyloid plaque immunoreactivity (TAPIR) and immunoprecipitation analysis. Results The total occurrence rate of anti-A? antibody was 27.8%. There was no significant difference of TAPIR positive rate in each age group. They had the similar immunospecialties to middle-aged and elderly healthy controls. Conclusion Plasma anti-A? antibody can be occured before amyloid deposits and senile plaques in brain.