Abstarct: Mashhad Subway third line tunnel is under construction on a 28 Km-Long route. The tunnel has been excavated by mechanized tunnelling method-EPB- with specific progress steps. Due to the existence of buildings with the old texture of the city and heavy traffic in this area, one of the important issues in this study is to Examine the settlement of the ground surface. In this research, Initially, the settlement due to tunnel excavation in the study area is estimated By Using Finite Difference FLAC3D software and the application of boundary and initial conditions, etc. Then, a comparison was made between the results of numerical modeling and instrumentation in the region, which shows that the maximum subsidence obtained from numerical modeling was 7.5 mm and the maximum settlement Wich recorded by the instrument in the region was 8 mm. Also, the sensitometry results of the settlement were evaluated to changes in the effective parameters of soil laxyers. In the following, the reliability of the settlement resulting from modeling is evaluated using the point Estimate method. For this purpose, three random variables of elastic modulus, angle of internal friction and cohesion of soil laxyers were selected and baxsed on the mean and standard deviation of each in each soil laxyer, 25 different data sets were formed. After determining the results of the modeling settlement of each of these data sets, the numerical modeling reliability index of 5.88 was calculated. In the last part of this study, By using an experimental method to calculate the maximum ground settlement, reliability assessment was performed by applying this relationship in the operating function and using RT software in two methods of first-order and second-order reliability. The Result of the reliability index evaluation using the first-order method Was equal to 1.52 and the second-order method was equal to 1.51. According to the results, the reliability index obtained from numerical modeling is larger than the experimental method and is at an acceptable level compared to global standards.