Abstract: Pre-Caspian Basin is one of the richest oil and gas basins in the world. Based on the thick salt formation of Lower Permian Kungurian, the entire section is divided into upper-salt strata and lower-salt strata. Block S is the main exploration target in the upper-salt strata. This block has experienced four exploration stages – evaluation, summarization, breakthrough and progressive and enlarged exploration – since it was acquired in 2004. The exploration effort was focused on inter-salt and salt canopy structural traps in the initial stage. Then the effort aimed at searching of producing reserves, such as ^“salt eaves^” trap, lithologic trap and salt canopy low-amplitude structural trap. The geological reserve is increased to 9050×10⁴t at the present time from 800×10⁴t at the purchase time. The analysis indicates that the success in exploration of Block S is based on the following aspects: analysis of old data served as the basis for making breakthrough in exploration of a new block and the proposed new conception of ^“salt eaves^” holding the key to exploration success. The evaluation method for finding clues to locate salt window, searching channels to locate the position, finding the buried depth to determine strata series and searching traps to determine positions of well is the cornerstone for high-efficiency exploration.