There exists a suite of ultrabasic-basic rock blocks in Luoji Village of Shangri-La County, whose nature is in debate. Petrologic studies show that this suite of rock blocks can be divided into two categories, one is of orthocumulate texture, and the other is of adcumulate texture. Petrologic geochemistry suggests that the rock blocks are low in alkali and oxygen fugacity, but high in calcium content. The original magma is proved to be of the sub-alkaline series with layer cumulate rock characteristics. Mineral composition and chemical composition of the clinopyroxene from ultrabasic-basic rocks suggest that the clinopyroxene is diopside and cation isomorphism is common. Temperature-pressure calculation implies that crystallization occurred under the condition of high temperature (1 084℃) and low pressure (0.15 GPa). The ultrabasic-basic rock blocks in the study area are products of mid-ocean ridge with the composition of oceanic curst, probably being the relics of Garze-Litang suture belt.