本文以阿胶为例对甲醛法[1]的精密度、稳定性及加样回收率进行了观察，首次将简便易行、测定结果准确的甲醛法应用于动物药的研究。通过对21种动物药饮片中总氨基酸的含量测定表明：炮制品相对于其生品中总氨基酸含量的变化，主要取决于炮制时间的长短。炮制时间控制在7min以内的样品，其含量高于生品．反之则低于生品。此结果为动物类中药的炮制研究提供了参考依据。 In this paper, the precision, stability and recovery rate of the formaldehyde method [1] were observed using Ejiao as an example. For the first time, the formaldehyde method, which is simple, easy to use and accurate, has been applied to the study of animal drugs. Through the determination of the total amino acid content of 21 kinds of animal medicine pieces, it is indicated that the change of the total amino acid content of processed products relative to their raw products mainly depends on the length of processing time. Processing time within 7min of the sample, its content is higher than raw materials. On the contrary, it is lower than raw materials. This result provides a reference for the research on the processing of animal medicines.