Abstract: The Laoshan granitoids, distributed in the middle part of the Northern Jiangsu-Southeastern Shandong tectonic zone, is a typical Mesozoic granitic complex composed of calc-alkaline and peralkaline groups. The calc-alkaline group includes three units of ganitic rocks: quartz monzonitic granite, biotite monzonitic granite and syenogranite unit, while the peralkaline group comprises a series of alkaline or peralkaline granites characterized by occurrence of alkaline melanic minerals such as arfvedsonite and aegirine. The emplacement ages determinated by zircon U-Ph method of the four above units are 146.8, 126.2. 113.0 and 110.8Ma respectively. There exists evident evolutionary trend indicated by increasing Si, alkaline and decreasing Al, Ca, Mg from quartz monzonitic granite, biotite monzonitic granite to syenogranite unit in the calc-alkaline group, while the alkaline granite is generally of higher Si, alkaline and lower Al, Ca, Mg and especially rich in Ga, Nb, Hf, Zr, Y and of high F/Cl, Ga/Al ratio, similar to typical A-type granite in the world. Based on the data of Sr, Nd, Ph, O isotope and the study of rock-forming mechanism, the authors presented that both groups of the Laoshan granitoids were derived from the similar source of metamorphic rocks of the lower crust basement, the Jiaonan Group, but related to two different partial melting events. In the first event, the calc-alkaline magma was generated to form three units by different degrees of fractional crystallization, while the alkailine granite was possibly generated from the remelting of the “restite” in the second event and through AFC process. Based on the results from a series of geochemical diagram and the regional tectonic development, it is suggested that the Laoshan granitoids are the products of a special period of tectonic evolution in the continent-continent collision transpression orogenic zone between Jiaobei terrane and Jiaonan terrane, of which the talc-alkaline group was formed at the compressive environment transpreesion or the transitiona1 environment from transpression to transtension, while the alkaline granite was definitely formed at the tensional environment. The latter can be considered as a mark of the ending of Mesozoic orogenic movement in the eastern Shandong area.