The oilfield of Xunyi-Yijun is located in the south of the Yi-Shan slope in Ordos Basin and is in its early stage of development. The formation unconformity contact cracks and stress cracks were formed due to the sedimentary environment of the Yanchang group of Triassic and the late tectonic movement, which makes it easy to lost circulation in the drilling and cementing process, resulting in insufficient return of the cement slurry; thus, the upper well section had not been effectively sealed. In this paper, the main factors for leakage are investigated by studying the geology, the drilling process and the drilling equipment, the slurry column structure and cementing technology in the oilfield. In order to improve the sealing quality of the oil and gas layer, the paper puts forward the anti leakage measures; optimizes the cement slurry formulation, which makes the slurry provide certain plugging performance; and modifies the slurry column structure and cementing process according to the “kill and seal” balanced cementing concept. After adopting the technical measures, the cement slurry return height and cementing quality of the oil and gas well in the job area met the requirements of the later fracturing treatment.