The survey was carried out in 4 districs of Phu Tho (Tan Son, Phu Tho, Cam Khe, Thanh Ba) to assess potential and actual situation using agronomic by-products as feeding for cattle in Phu Tho by questionaire. The results show that, potential of agronomic by-products (mainly are rice straw, maize stover, cassava hay) in Phu Tho are huge but it do not using thoroughly in cattle production. Rice straw are used the commonest with 71 percent, cassava hay are the least common with 1 percent. However, almost byproducts are used on unprocessing form. There are only 12 percent farmer process rice straw, 8 percent process maize stover as cattle feeding. Applicate some current technical advances to improve economic efficiency in cattle production show that, the average daily gain of cattle in experiment diets are faster than cattle in diet without processed byproducts. Profit are also increase significantly when using processed byproducts in cattle diet because of reducing feed expenditure per weight gain. In conclusion, processing and preservation agronomic byproducts as cattle feeding rose economic efficiency in cattle production significantly.