Abstract: The free iron oxide in loess is one of important climate proxies of the summer monsoon. It is a complicated process to extract it by classical CBD method. Moreover, extraction results are very different in different experiment conditions. Experiment for extraction of free iron oxide by hydroxylamine and different concentrated hydrochloride-acids in diverse conditions has been studied. The results show that the temperature is the ultimate effect of this experiment, and the concentration of hydrochloride-acid is subordinate. Comparing it with classical CBD method, we can choose the optimal substitution of CBD and simplify the experiment process.