Picrite in island arcs has been rarely reported.However,several thick layers of picrite,which were rarely found in the world,were recognized in the Middle Devonian strata on the southern margin of the Altay Mountain. this paper presents new data of electronic microprobe analvses on clinopyroxenes from the layers of picrite and associated basalt in this area. It is shown that the clinopyroxenes from the picrite are exclusively diopside, whereas those from the basalt are diopside and augite, suggesting a continuous variation in composition. The crystallization temperature, pressure and depth of clinopyroxene phenocrysts from the picrite and basalt were calculated on the basis of the clinopyroxene-melt equilibrium principle. The temperature of mineral crystallization in depth, which represents the condition of picritic magma chamber, is estimated to be in the range of 1350~1387℃, and the corresponding pressure and depth are 16.6~21.3 kPa and 55~70 km, respectively. In contrast, the depth of mineral crystallization in the shallow part, which represents the condition of basaltic magma chamber, is in the range of 37~41 km, indicating that the basaltic magma might have been an mineral chemistry of the clinopyroxenes shows that the volcanic rocks in this area belong to subalkaline series and were probably formed in and island arc setting.