Abstract: Abstract: In past few years, a new irrigation method is developed, which is trace quantity irrigation. Trace quantity irrigation is based on the capillary phenomena and membrane filtration technology, can completely solve the problem of emitter clogging and achieve the "self-adaptive irrigation" (water supply following crop demand), and has higher water utilization efficiency. In this study, we queried about theory and technical properties of trace quantity irrigation. The analysis showed that: 1) According to the basic characteristics of the capillary, and the actual condition of trace quantity irrigation emitters and low flow point-water source, the capillary force cannot be the basis for irrigation systems; 2) Soil water potential is not equivalent to negative pressure, the former is not yet be perceived by dripper outlet, and the "adaptive irrigation" that trace quantity irrigation realizes the match of crop water requirement with irrigation amount was still lack of evidence; 3) It was hasty to draw the conclusion that filter membranes and fiber emitter channel cannot be clogged for a long time; 4) As a subsurface irrigation method, the effects of water-saving, anti-clogging, and yield-increasing of trace quantity irrigation should be confirmed in a long term experiment (at least 4-5 years based on experience); and 5) According to the common perception of international micro-irrigation field, the irrigation product with flow not greater than 12 L/h is referred to as the dripper, and thus the trace quantity irrigation should be attributed to subsurface drip irrigation with the dripper of membrane and fiber bundle structure. It is no double that the trace quantity irrigation is a good try for the lower flow water supply and membrane filtration in subsurface irrigation systems. However, the statements that the trace quantity irrigation can achieve the "self-adaptive irrigation", which will revise the field of crop cultivation and water conservancy of agricultural field, and lead the next round of innovations for irrigation technique are questionable. In summary, the trace quantity irrigation as a technique is of many shortcomings in the theory and techniques, and has a high risk of failure. This technique is currently in a stage of principle exploring. The urgency is to clarify its theory and verify it in small areas. The technique is still far from pilot production and large-area promotion.