Abstract: At China?s current exploration and development stage, assessment of tight oil resources can preferably adopt three convenient methods, namely analogous method for abundance of resources, EUR analogous method and volumetric method for small area. Two additional methods for more detailed assessment can be used in some areas where exploration degree is relatively high, namely, method for prediction of spatial distribution of resources and method for numerical simulation of hydrocarbon accumulations. This article briefs about the principles of former three methods, assessment process, key parameters and conditions for application and selects tight oil from Yanchang Formation of Ordos Basin as the case for study. The characteristics of those three methods are shown on the basis of application and comparison. The application results confirm one another, indicating a great potential of tight oil geological resources in Yanchang Formation. With the recoverable reserves estimated at (4~6)× 108t, Yanchang Formation is indicated as the most important tight oil exploration target in China at the present time.