In allusion to the problems encountered in research such as the complex distribution of residual middle-lower Jurassic，inconsistent knowledge about original depositional filling，etc.，the residual strata distribution of the middle-lower Jurassic was made clearly according to the Jurassic outcrop profile，drilling and seismic data and combined with the technical methods including drilling calibration，seismic facies analysis and low velocity anomaly detection. Strata sedimentary characteristics and evolution law of filling during Early-Middle Jurassic were studied systematically by field geological profile measurement and core description. Palaeo-sedimentary system of the middle-lower Jurassic in the study area was recovered combined with evolution relationship between Meso-Cenozoic basin and mountain. The research results show that the residual lower Jurassic distributed only in Hongshan sag of eastern Qaidama Basin with an area of about 640 km2；the residual middle Jurassic distributed in six sags such as Hongshan-Xiaochaidan，Gaxi-Yuqia，Hobson and Delingha，and the middle-lower Jurassic did not appear in Gaqiu，Dachaidan and Ounan areas. The depositional filling systems in Early Jurassic of eastern Qaidam Basin are characterized by alluvial fan，braided river，braided river delta，shallow lake and braided river delta，and their source came mainly from north Qilian mountain，secondarily from the south Chainan Uplift. The middle Jurassic developed while Qaidam Basin depressed and its depositional systems changed as follows：fan delta，braided river delta and sub-lacustrine transgressive cycle.