The purpose of this study was to determine the auxiliary raw material inventory control by PG. Ngadirejo Kediri and determine the auxiliary raw material inventory control using Economic Order Quantity. This type of research is descriptive research with quantitative approach. Source of data in this research using secondary data sources obtained directly from the company. Collecting data using interviews and documentation. Analysis of the data used in this research using Economic Order Quantity. Result of the analysis proves that when companies apply the method Economic Order Quantity in 2013, 2014, and 2015 in the purchase of raw materials auxiliary optimum, so there are the difference of spending cuts total cost for raw materials auxiliary belerang consecutive Rp. 1.010.959,19574, Rp. 957.208,54419, Rp. 1.165.215,68373. So also the raw material phosphate auxiliary in 2013, 2014, and 2015 there were a total savings respectively of Rp. 2.961.990,3358, Rp. 2.764.054,70668, Rp. 3.374.978,66496. Based on the analysis conducted, it should be PG. Ngadirejo Kediri apply method Economic Order Quantity in determining the quantity of the purchase of raw materials auxiliary materials optimal, so as to minimize total cost incurred by the company every year.