The present paper deals with the study of diversity of Zooplanktons and their seasonal variation of density in the GulabSagar water body, Jodhpur. Samples were collected for a period of two years (May 2014-April 2016) at each month and collected samples were evaluated for the study of Zooplankton. In the present study the zooplanktons consisted of Rotifers, Ostracods, Cladocerans and Copepoda. The quantitative estimation shows that in both the yearsof study (2014 - 2015 and 2015 - 16) the Rotiferans dominated in the population while other wereencountered with moderate number.The study also reveals that during seasonal variation the Rotiferans dominated mainly in the winter season in both the years of study which can be due to favourable temperature and availability of abundance of food material. In the present study the Zooplanktons were represented by 41 species and consisted of Rotifera (15), Cladocera (21), Copepoda ( 4 ) and ostracoda ( 1). The quantitative relationship among different groups of Zooplanktons during year (2014 - 2015) was Rotifera>Copepoda>Cladocera>Ostracoda. During the year (2015 - 2016) the above relationship was Rotifera>Copepoda>Cladocera>Ostracoda.