Abstrak. Penelitian ini bertujuan untuk menguji aktivitas fraksi etil asetat kirinyuh terhadap pertumbuhan bayam duri dan manfaat dari ekstrak kirinyuh. Penelitian ini dilaksanakan di Laboratorium Ilmu Gulma Jurusan Agroteknologi Fakultas Pertanian, Laboratorium Analisis Kimia Fakultas Matematika dan Ilmu Pengetahuan Alam (FMIPA), dan Kebun Percobaan Fakultas Pertanian Universitas Syiah Kuala Banda Aceh, mulai September – Desember 2018. Bahan yang digunakan dalam penelitian ini adalah daun kirinyuh, benih bayam duri, aquades, herbisida 2,4 D, amonia 70%, pelarut n-heksane dan etil asetat, kertas label, kapas, air, pupuk kandang dan tanah. Alat-alat yang digunakan adalah pisau, lesung, wadah kaleng, saringan, kapas, karung goni, corong, Aluminium foil, penggaris, jangka sorong, Rotary evaporator, timbangan analitik, ayakan pasir, pot volume 1 kg, keranjang, tempat penampung air, Leaf area meter, oven, kamera, dan alat tulis. Penelitian ini menggunakan Rancangan Acak Lengkap (RAL) non-faktorial dengan 5 perlakuan; C0 = kontrol; C1 = 5%; C2 = 10%; C3 = 15%; C4 = 20% ekstrak kirinyuh yang diulang sebanyak tiga kali, sehingga terdapat 15 satuan percobaan. Setiap ulangan terdiri dari 4 pot dikarenakan sifat destruktif. Hasil penelitian menunjukkan pada uji fitokimia ditemukan senyawa alkaloid, steroid, saponin dan fenolik. Pemberian ekstrak etil asetat kirinyuh berpengaruh pada laju tinggi gulma, jumlah daun gulma dan persentase pengendalian gulma. Kata kunci : ekstrak, kirinyuh, bayam duri dan konsentrasi. Abstract. This study aims to obtain the activity of ethyl acetate essentials fraction from siam weed extract on the growth of spiny amaranth and the benefits of the siam weed extract. . This research was conducted in Weed Science Laboratory and Experimental Garden Department of Agrotechnology, Food Analysis Laboratory Department of Food technology Faculty of Agriculture, Chemical Analysis Mathematics and Natural Science faculty, University of Syiah Kuala, Darussalam Banda Aceh, from September - December 2018. The materials used in this study were leaves of siam weed, seeds of spiny amaranth, aquades, herbicide 2,4 D, ammonia 70%, solvents n-hexane and ethyl acetate, label, cotton, water, cowdung and soil. The tools used are knives, mortar, canned containers, filter, cotton, gunny sacks, funnels, aluminum foil, rulers, calipers, rotary evaporators, analytical scales, sand filtes, 1 kg volume pots, baskets, water reservoir, leaf area meter, oven, camera, and stationery. This study used a non-factorial Completely Randomized Design (CRD) with 5 treatments; C0 = control; C1 = 5%; C2 = 10%; C3 = 15%; C4 = 20% siam weedextract was repeated three times, so there were 15 experimental units. Each test consists of 4 pots due to destructive nature. The results showed that the phytochemical test found alkaloid, steroid, saponin and phenolic compounds. Giving ethyl acetate extract has a significant effect on the high rates of weeds, weed leaf number and weed control percentage Keywords : extract, siam weed, spiny amaranth and concentration.