Objectives:The Yidun Arc is a Triassic volcanic arc located between the Songpan Garzê Fold Belt and the Qiangtang Block, southwestern China. Daocheng Pluton and Haizishan Pluton which outcroped in the Yidun Arc are late Triassic and Cretaceous granitic plutons, respectively. Methods: In this paper, we combine petrogeochemistry with systematic mineralogical characteristics of the plutons mentioned above by means of petrological observation, electron microprobe analysis and scanned eletron microscope. Results:The results show that: the two granitic plutons are mainly composed of plagioclase (andesine—oligoclase), Kfeldspar(orthoclase),quartz and biotite(siderophyllite—iron biotite),and the accessory minerals include zircon, sphene, magnetite and apatite; the chemical composition of biotites shows that the parental magma for the two granitic plutons was a hybrid melt possessed depleted mantle and typical crustal source. Daocheng Pluton shows the features of high-K calc-alkaline with peraluminous characteristics, whereas Haizishan Pluton belongs to high-K calc-alkaline to shoshonite series with peraluminous feature. The temperature of the two plutons were limited according to two geothermometers. The average upper limit temperature of Daocheng Pluton were 783℃, and the average upper limit formed temperature of magma of Haizishan Pluton was 844℃. Conclusions：In combination with previous studies on magmatism in the Yidun Arc, we think that Daocheng pluton belongs to high fractionated I-type granite, and we propose that the source for the Daocheng granite which probably derived from a Late Paleoproterozoic to Early Mesoproterozoic lower crust material related to Yangtze Craton, underwent the partial melting of the lower crust triggered by the underplating of large-scale mantle-derived magma under the syncollisional tectonic setting following the westward subduction and closure of the Garz —Litang paleoocean. The generated hybrid melts which including lower crustal magma and minor depleted mantle-derived magma intruded in middle—upper crust and gave rise to the Daocheng granite because of the density. Daocheng granite then underwent rapid cooling and had cooled to below 300℃ by the beginning of the Jurassic. Haizishan pluton was an A2type granitic pluton and likely to form under postcollisional extensional tectonic setting related to arc—continent collision during the Early Cretaceous. As same as Daocheng granite, the source melt of Haizishan granite also included crustal magma and minor mantlederived magma, these hybrid melts thereafter were continuously injected into a shallowlevel chamber and experienced rapid cooling, suggesting they were emplaced at shallow crustal depths.