Rock mass characterization is one of the most important parameters affecting the underground mine design. This study deals with the prediction of rock mass quality using geo-statistical estimator in Anguran underground mine at the level +2740. For this, a database consisting of 427 Q-based rock mass quality data sets was developed during the development of mine drifts. Accordingly, data were analyzed and checked for normality, trend and anisotropy. Analysis on Q-data showed that: 1- they do not have a normal distribution, 2- there are neither global nor local outliers in data 3- the data seem to exhibit a trend. In this study, the Universal Kriging was used due to existing trend in datasets. Taking into consideration five estimation error evaluation criteria, the best Variogram model was selected among three models: exponential, spherical and Gaussian. The results showed that spherical variogram model provides the best fit to the data's spatial structure. Cross validation showed high accuracy level for performance of geo-statistical estimator. Accordingly, the rock mass quality map for the area under study built in ArcGIS environment. The analysis results of final rock mass quality map revealed that about 53% of under study area has poor to extremely poor rock mass condition, 8% has fair and 39% has good to extremely good rock mass condition.