Cabbage is one of most economic agricultural commodities in Bali. On the other hand to produce cabbage base on consumer want is very difficult. The lost of yield of cabbage is causing by diseases and pests. The most serious disease has been reported, it is club root (Plasmodiophora brassicae) and the most important pest is diamondback moth (Plutella xylostella) (Shepard, et al. 1999). The population of P. xylostella is very high on dray season. To control P. xylostella have been conducted by using chemical pesticides. However the chemical pesticides have been known dangerous to environmental as well as human being. If we do not use properly this chemicals can be cause the resistance of the insect, resurgence, and contamination to environmental (Suprapta, et al. 2003).To minimizing the effect of chemical pesticide, some considerations were created, one of them is using of bio-pesticides. Some of bio-pesticide has been found from essential oil. (Sumiartha et. al. 2005; Sudiarta et al. 2006). The one of potential essential oil to use as bio-pesticide is lemongrass. Sila Adnyana et al. (2011) reported lemongrass was utilized to control hairy caterpillar. The result show, the caterpillars were lethal totally in 5 minute after treatment by lemongrass on the concentration of 0.5%. According Adeniran and Fabiyi 2012 lemongrass was investigated to control mosquito and sugar ant. On the other hand lemongrass oil was reported has the repellent activity to Callosobruchus maculates (Paranagama et al., 2002). Base on the data the lemongrass is very potential to utilize as biopesticide. To utilize lemongrass as bio-pesticide, the important information of effication of lemongrass to P. xylostella and Phytotoxicity of lemongrass to cabbage are needed. Therefore the study was conducted in order to analyze the effication of lemongrass to P. xylostella and Phytotoxicity of lemongrass to cabbage.