This study aims to determine the amount of transformer production, availability of labor, inventory of finished products, normal working hours and optimal overtime so as to obtain minimal production costs and increase company profits. The method used in this study is to use Aggregate Planning by optimizing mixed integer linear programming. The data used is the secondary data of the company, then developed with mathematical models and processing data using the help of LINDO 6.1 software. The results of the study are as follows: 1.) The optimal number of production at (normal working hours and overtime) is 141 units of product, 2.) The optimal number of workers is that there are 173 employees or companies do not need to increase or decrease the number of employees, 3.) The optimal number of finished product inventories is 69 units. 4.) The need for normal working hours and optimal overtime decreases from 201,541 to 193,755 people working hours or decreases by 4%, 5.) Optimization of minimizing transformer production costs is 4.6% or Rp. 57,661,862,889, - from Rp. 1,249,002,284,528, - to Rp 1,191,340,421,639, -.