Abstarct: Pipe is one of the structures which is used in fluid transfer. Pipes are divided in two types: straight and curved. Curves are used to redirect the pipes. The most common type of bends that are widely produced and have industrial applications are bent with 45 degrees, 90 degrees and, 180 degrees. In addition, they have circular, rectangles and squares cross sections. One the important issues in the design of pipes is pressure drop. According to the fact that the pressure drop in a pipe bend is higher than that of straight pipe with the same specifications; investigating the pressure drop in the pipe elbow is very important. Researchers always have tried to minimize pressure loss in the elbow. The results showed that factors such as the radius of curvature than the radius of the pipe and the angle of bends affect the pressure drop of pipe bends. One of the solutions that have been used to reduce pressure drop in the pipe bends is to implement guide vane that could significantly reduce pressure drop in the pipe bends. In This research, the effects of bends angle on the pressure drop in pipe bend is investigated using Fluent. Furthermore, variety parameters like elbow with or without guide vane and different radius of curvature to the radius of the bend ratio such as 1.5, 2 and, 3.6 are studied. Also, all results are compared with experimental results and showed a good agreement with them. This study shows that increasing the angle of bend, rises pressure drop coefficient in pipe bends and applying guide vane can reduce the pressure drop by 50%. In addition, the effect of the Reynolds number on the drop pressure is studied and results showed that by increasing the Reynolds number, pressure loss coefficient decreases and the guide vane is a very effective method to reduce pressure loss coefficient.