In the present study, the effect of two different co-solvelts including acetone and hexane, were considered in ultrasound-assisted synthesis of biodiesel from Jatropha oil in the present of CaO as catalyst. First of all, some important physicochemichal properties of jatropha oil including, Fatty acids composition, water content(2% w/w), Free faty acid (34 %), Soponification value(197.02 mg.g-1), density(0.899 g.cm-3), refrect index(1.466), Viscosity(38.6 mm2.s-1) and iodine value (100 g.g-1) were meatured in acordance with AOCS standards. Oleic and linoleic acid were the main fatty acids in the jatropha oil. Due to high acid value of the oil, esterifacation reaction was carried out using sulfuric acid (1%) and methanol oil molar ratio of 9:1 durong 120 min under reflux sysytem. In ultrasound-assisted synthesis of biodiesel all experiments were performed with a probe type ultrasound instrument (UP 200 H) in the constant frequency (20 kHz), output power (200 w), cycle (0.7) and resonance amplitude (70%). Results showed that the presence of co-solvent has significant effect on improving of the transesterificatio reaction. This is due to increase miscibility of the reactants and efficient contact between them. Among the two considered co-solvents, acetone was the better one due to its polarity which is well between oil and methanol. In optimum operating condition including acetone to methanol of 25% v/v, methanol to oil molar ratio of 12:1, catalyst to oil of 4% w/w, time of 1 h and temperature of 55 C, a conversion yield above of 90% was obtained. Fethermore in this study 1 liter biodiesel from Jatropha oil with conversion rate of 92.31% was successfully synthesized via common heating-reflux synthesis method with NaOH as catalyst, under optimum operatin condition acocordance with the literatures. The analytical methods used in this study were Hnmr and GC-FID. Also some physical and chemichal properties of synthesiszed biodiesel such as dendity, viscosity, water content, refrect index, acid and iodine value were determined that was in agreement with the literatures. Also the studies show that the biodiesel industry from the Jatropha oil is economically viable.‎