Abstract: Tides attract humans’ attentions since thousands of years and observed as a phenomena affected by celestials and terrains parameters. The Nahr-El-Qasr, Latitude 32.00 N and Longitude 53.00 E, (see reference x) station situated in the heart of El-Qasabah and represents the tidal effects and water level fulctuations of the boundary river Arwand River. In this paper data of the water height for eight months from January 1998 to September 1999, in Nahr-El-Qasir, investigated. We applied spectral analysis to determine the tidal constituents. At first the water height data arranged in a time series form then using FFT method we find twenty four tidal constituents including MSf ، Mf ، 2Q1 ، Q1 ، Rho1 ، O1 ، M1 ، P1 ، K1 ، J1 ، OO1 ، 2N2 ، N2 ، Nu2 ، M2 ، Lambda2 ، L2 ، T2 ، K2 ، 2MK3 ، MK3 ، MN4 ، M4 ، MS4. The strongest component is Mf which shows that the main fluctuations are due to the astronomical origin. However considering f-number in American scale which is 1.43 the dominant tide is mixed and because of many tidal constituents with periods that are not recognized as standard periods, we can say that study area is strongly affected by the local parameters.