Pollution is a problem for most of the territorial waters in Indonesia including the territorial waters on the coast of Seger Kuta, Central Lombok, originating from the Bau Nyale Tradition activities. One way to analyze the quality of waters in coastal areas is to conduct analysis of water quality in terms of parameters, physics, chemistry and biology. This method can provide information about water conditions in accordance with its designation. The purpose of this study was to determine the condition of the quality of the waters of the Seger Coast before and after the tradition of the nyale odor based on physical, chemical and biological parameters. This research was conducted in February 2020 at three research stations, then the results were compared with sea water quality standards based on Minister of Environment Decree Number 51 of 2004 concerning Sea Water Quality Standards and other references. The results showed in general the quality of coastal waters before and after the tradition of nyale odor at Seger Kuta beach, Central Lombok is still classified as good or lightly polluted waters based on seawater quality standards for marine biota in the Decree of the Minister of Environment NO 51 of 2004 and references others. While for the results of Plankton found in the study site before the Nyale odor tradition, there are 8 genera from 4 phytoplankton groups, namely Diatomae 5 genera, Dinophyceae 1 genus, Cynophiceae 1 genus and Cilliata 1 genus. the tradition of nyale odors ranges from 6-8 genera with a total abundance of 95-227. While after the Nyale odor tradition there are 8 genera from 3 phytoplankton groups, namely 6 genera Diatomae, 1 genus Mastigophora and 1 genus Cynophiceae. The number of genera from each station after the Nyale Odor tradition ranges from 7-8 genera with a total abundance of 62-171. Keywords: Before and After Bau Nyale Tradition Activities, Water Quality, Seger Kuta Beach, Central Lombok NTB.