Abstract: The 6^th member of Yanchang Formation of Jurassic System in the northern region of Shaanxi is an important layer for oil exploration and development. High natural gamma sandstone is widespread in this layer. Such reservoir is different from conventional one in terms of logging response characteristics, thus causing some difficulties for calculation of physical property parameters and water saturation logging for the 6^th member of the formation. Based on comparison and analysis of logging characteristics between the high gamma reservoir and its neighbor conventional reservoir, the formula is established to calculate porosity, permeability and mud content for the 6^th member of Yangchang Formation. This paper also further discusses the horizontally oil-bearing property of such reservoir. High gamma reservoir is nor obviously different from its neighboring conventional reservoir in terms of core analysis of saturation. However, high gamma reservoir is quite different from its neighboring conventional well in terms of water saturation calculated by using logging data, because the resistivity value of high gamma reservoir decreases significantly. Therefore, the saturation calculation formula of high gamma reservoir is revised. Based on classification of reservoirs, this paper regards changes of resistivity and porosity of high gamma reservoir as the main factor to affect saturation calculation of the 6^th member of Yanchang Formation in the northern region of Shaanxi. The formula is further perfected for saturation calculation of the complicated 6^th member of Yanchang Formation in this region.