Chalcones is a very interesting compounds because it is known to have various of biological activities such as antimicrobial, antifungal, anticancer, antimalarial, antioxidant, antitumor, anti-inflammatory and antidepressant. Moreover, natural and synthetic compounds of chalcones have roles as precursors for other compounds. Therefore, many chalcones become model structures of target compounds by researcher. In this research, methoxy chalcones derivatives have been synthesized using stirrer method and using base catalyst NaOH. The synthesized results obtained are (E)-3-(4-isoprophylphenyl)-1-(4’-methoxyphenyl)prop-2-en-1-one (1), (E)-1-(4’-methoxyphenyl)-3-p-tolylprop-2-en-1-one (2) and (E)-3-(3-bromophenyl)-1-(4’-methoxyphenyl)prop-2-en-1-one (3). The purity of all compounds have been tested using TLC, melting point test, analytical HPLC. Then they are characterized using UV, FTIR, ¹H-NMR and MS spectroscopy. The toxicity assessments of the novel compounds were done by Brine Shrimp Lethality Test (BSLT) method. The all compounds showed very good activity with LC₅₀ value<200 μg/mL.