This paper attempts to investigate the relationship between the sampling interval and the order of Autoregressive model for estimating the properties of three dimensional surface roughness by use of computer simulation. To check the validity of the order of AR model and the sampling interval, a comparison of the postulated model with the computer simulation was carried out on the number of the zero-crossings, the peaks and the density of summit of the three dimensional surface model. As a result of computer simulation, the suitable order of Autoregressive model for estimating properties of surface roughness is considered to be 7th less than FPE estimation. It is also suitable that the sampling interval is divided a asperity into about 10.