The intervals  between salt beds in the Qiangjiang Formation of Upper Eocene-Lower Oligocene of Paleogene consist of sandstones and non-sandstones. The  non-sandstones are widely distributed and mainly composed of mm- scale to cm- scale of single bed ,a total of several decimeter to several meter thick salt-bearing rhythms , most of which are polymictic mixed rocks composed of evaporite minerals, carbonate minerals and terrigenous clays and fine clastic minerals. For a long time, the study of the non-sandstones between salt beds has been limited to the lithological character and less attention has been paid to sedimentary characteristics and sedimentary environments, Through the detailed study on the cores of three wells, a total of 151m thick in Wangchang Structure of northwestern Qianjiang Sag,  this paper gives a systematic analysis of the sedimentary characteristics and environments of the intervals between salt beds,  and suggests  that the lake  basin was a perennial relatively deepwater meromictic salt lake which can be roughly divided into brackish-water lake, semisalt-water lake, salt-water lake, and brine lake when the intervals between salt beds were deposited. During the peroid of Qianjiang Formation deposited the waterdepth of lake basin was gradually from deeper to shallower.