From comparison with west Chaidamu basin in climate condition, saline mineral distribution and brine reservoir in clastic stratum, in combination with the brine reservoir discovery in graben fault depression, the paper proposes that the deep stratum in Lop Nur has potassium prospecting. The deep potash resources are investigated in Northwest Luobei depression of Lop Nur. And the first deep well (well LDK01) to prospect potassium in Lop Nur lake is implemented, in which potassium mineral including glaserite, Kalistrontite and erythrosiderite are discovered for the first time. The potassium mineral including sylvite, carnallite etc. are discovered in deep clastic stratum, in which the maximum proportion of KCL is 2.86%, which reveals that low grade solid potash resources are reserved in deep stratum. A new type of potassium mineral, clastic potassium is discovered, which expand orientation and space for potassium prospecting in Lop Nur. The average grade of KCL in deep clastic stratum is 1.5%, which reveals that there is potassium-rich brine in deep Lop Nur lake. Gravity detecting found that secondary depression is developed in west Lop Nur basin. it’s preliminary estimated that the quaternary sedimentary thickness is more than 1200m. From geological analysis, it’s predicted that the fault basin in front of Kuruketag mountain and Luobei depression are key target for deep potassium prospecting. In combination of remote sensing, geophysical and physical property data, it’s estimated that the potash resources in deep Luobei depression can be up to 160million ton. The paper also proposes that rich potash resources are reserved in deep stratum in west of Luobei depression and surrounding region. There is large potash potential in deep Lop Nur lake. This discovery has important significance for further studying the formation and evolution of Lop Nur lake and large scale of potash production for potash fertilizer enterprise.