The weirs are the simplest, least expensive and most accurate hydraulic structures for controlling and measuring water flow in open channels and differet shapes. The most common types of weirs are trapezoidal broad-crested weirs because of the high precision in determining amount of discharge. When designing weirs, hydraulic design parameters are very important and the most important parameters are velocity and pressure. In this study, the hydraulic characteristics on two broad-crested weirs were considered at the Hydraulic Laboratory of Isfahan University of Technology. Flow profiles, velocity profiles over the upstream and crest and pressure along the weir were investigated. Two models were up 30 -down 45 and up 45 -down 30 . Three expriments were conducted on each weirs and mentioned parameters were taken for three discharges of each models. Laboratory results of water surface profiles showed with increasing discharge, the critical depth is transmitted to the upstream of crest and decreasing the upstream face slope, transmitted the critical depth to the downstream of crest. Laboratory results of velocity showed with increasing discharge, velocity distribution on the crest become more uniform and velocity near the floor is maximum and near the water surface is minimum. Decreasing the upstream face slope, increased velocity in the heel of weir and velocity over the crest become uniform. Laboratory results of pressure distribution showed that in the upstream of the crest, decreasing discharge, decreased pressure and in the downstream of the crest, decreasing discharge, increased pressure. Then, using the FLOW-3D software and utilizing the RNG K-e turbulence model, the flow over broad-crested weir was simulated for six existing experiments, and numerical results and experimental results were compared. The results showed a high agreement between numerical and experimental results. By simulating different models, flow hydraulic parameters such as boundry layer, flow separation, discharge coefficient and pressure were considered. Increasing the upstream face slope, increased boundry layer thickness and maximum of boundry layer thickness transmitted to downstream of the crest. Change in downstream face slope doesn't have much effect on boundry layer thickness. Increasing discharge, decreased boundry layer thickness. Decreasing upstream face slope, decreased separation zone discharge coefficient increased. Change in downstream face slope doesn't have much effect on separation zone and discharge coefficient. Analyzing the pressure on the crest showed that increasing the downstream face slope, decreased pressure on the crest and the probility of occurrence of cavitation increased but it doesn't have much effect on pressure in the upstream face slope. Results showed that with decreasing upstream face slope, the slope of the drop in pressure is reduced. Increasing upstream face slope, reduced pressure in the upstream of crest and increased pressure in the middle of crest. Key words : Broad-crested weir, Flow profiles, Velocity profiles, Pressure distribution, FLOW-3D, RNG K- turbulence model.