In this paper, the authors describe the rock assemblage series and geochemical characteristics of the intra-oceanic arc and initial arc during the ocean-continent transition, and propose that the magmatic arc was formed together with the ocean-continent transition and the underplating crust-mantle transition. The former arc environment was the place where the primary continent was formed by the ocean-continent transition, which constituted diagnostic basalts of former arc of intra-oceanic arc similar to the midoceanic ridge. The formation process of the continent is as follows: the oceanic crust grew from the mantle, and the immature arccontinent crust grew from the ocean-continent transition in the oceanic crust: at last, the mature continent crust grew from the curstmantle transition of underplating arc-continent crust. Therefore, the growth and formation of the earth's crust was mainly realized by the accretion of magma.