The research studied abaut on economic analysis of fattening the aceh bull using the substitution of elephant grass with the fermentation of water hyacinth had been done in the laboratory of animal husbandry, study program of agriculture faculty syiah kuala university. this research had been done for 112 days, from january 24 to may 8 2016. the purpose of this research is to know the influence of giving pasture grass for cattle feed substitution of elephant grass with fermentation of water hyacinth to the efficiency of caring aceh bull. the material of this research was taken from four aceh bulls and using latin square design (lsd) which consists of 4 characteristics and 4 repetitions. each of its characteristic a (60% elephant grass and 0% is fermentation of water hyacinth), the characteristic b (50% elephant grass and 10% is fermentation of water hyacinth), the character c (40% elephant grass and 20% is fermentation of water hyacinth), and character d (30% elephant grass and 30%