Always Gas and liquid fluids play a significant role in the industry. The volume of passing is very important in different industries. Therefore, the industry uses high-precision flowmeters such as ultrasonic flowmeters. In this research, the purpose is to investigate single-phase and two-phase flowmeters. The effect of environmental factors such as temperature and pressure on the performance accuracy of single-phase water flowmeters is investigated. For this study, Comsol software is used which can simulate two acoustic environments of moving wave propagation and fluid. With this application referred to in simulated interactions between the environment and the speed of the fluid enters the water at different temperatures and pressures must be measured. One simulation is used to investigate the performance of the flowmeter converter in the stationary fluid and another simulation is used to evaluate the effect of temperature and pressure on the flowmeter of the flowing fluid. The error due to measuring the velocity of sound in the stationary fluid is reported to be less than 1.5%. Finally, the two simulations are combined and the effect of temperature and pressure on the correction factor of velocity profile and received voltage is investigated. The appropriate temperature range for starting the flowmeter is 20 to 70 degrees Celsius and the fluid pressure is higher, a stronger wave is received at the receiver. Keywoords Single phase flowmeter, ultrasonic flowmeter, ultrasonic flowmeter, correction factor flow profile, COMSOL simulation, transient time , Acoustic water impedance, Multiphysics problem