Aiming at the leakage and diffusion problems of the 35 MPa ultrahigh pressure gas pipeline in densely populated area, the FLUENT software in the threedimensional numerical simulation was used under different climate conditions in the deep buried gas pipeline leak case. And the axial and surface safety area of the hydrogen sulfide and methane was provided when the ultrahigh pressure gas pipeline had leaked under the conditions of different wind speeds. Because of the buoyancy, the natural gas developed in the upward form during the process of diffusion. The wind speed and pressure had different effects on the diffusion process under the different environments. The result was that as the wind speed and pressure was higher, the natural gas was spread to the farther distance. This increased the lowest explosive limit and alerted the concentration range of the natural gas. The research result could provide the effective basis to the stuffs and security management in leakage spot.

Because of the natural life of the pipeline and the impact of artificial factors, pipeline leakage accidents occur frequently. It is very important to detect pipeline leaks and determine the leak location to minimize damage and maintain the safe operation of the pipeline. Be aimed at the products pipeline leak, the CFD simulation software was used to simulate changes in the pipeline pressure. Once the pressure changed at the pipe end and beginning, the pipeline leak happened somewhere. Then under the pressure gradient changes of the pipeline end and beginning, the pressure gradient method was used to ultimately determine the leak location of the pipeline. 

In flow measurement field, the differential pressure flowmeter was used widely. Adopting highprecision calibration system to calibration differential pressure flowmeter，the flow coefficient of the flowmeter was obtained. And the error analysis of the flow coefficient with scientific method was made to draw calibration result and its error accuracy. The results show that the measurement errors of the flowmeter followed the standard, and the flowmeter could be used for the actual measurement in the field.