In this research، efficacy of Thymus persicus (Roniger ex Reach F.) and Prangos acaulis (Dc.) Bornmessential oil was investigated against egg hatching larvae and adults of Callosobruchus maculatus (F). This experiment was performed at 27 ± 1 °C and 60 ± 5% R. H. under dark condition. Concentrations tested included six concentrations (of 0. 36 - 3. 57 µl/l air) for 1 and 4-day old eggs hatching، six concentrations (1. 78-8. 92 µl/l air) for 1، 7 and 14 days larvae and four concentrations (51. 9-340. 7 µL/L air) for adults at five replications. Increasing the essential oil concentrations resulted in increase of insecticidal activity on eggs، larvae and adults. Based on LC50 values calculated for eggs and larvae، ovicidal and larvicidal activity of T. persicus was not significantly different with that of P. acaulis essential oil. Moreover، this activity did not differ between 1 and 4-day-old eggs. Toxic effect of the oil was reduced as larval stage increased، showing that older larvae could be more resistant than younger larvae. At the highest concentration (370. 4 µl/l air) essential oil of T. persicus and P. acaulis caused 100% of mortality in adults after 6 and 4. 5 hours، respectively. LC50 values of T. persicus (2. 39 µl/l air) were siginificantly higher that P. acaulis (1. 31 µl/l air). Results showed that these essential oils were effective and can be used as a potential control practice against cowpea beetles.