Microtwins in the 3C-SiC films grown on Si(001) by atmosphere pressure chemical vapor deposition(APCVD) were investigated in detail using X-ray four-circle diffractometry. The Φ scan shows that 3C-SiC films can grow on Si substrates epitaxially and epitaxial relationship is revealed as (001) 3 C - S i C (001) S i , [111] 3 C - S i C [111] S i . Other diffraction peaks at about 15.8 o in x emerged in the pole figures of the (111) 3C-SiC. We performed the pole figure of (1010)h-SiC and the reciprocal space mapping from the (111) reciprocal lattice point of base SiC to the (002) point of microtwin for the first time, indicating that the diffraction peaks at 15.8 o in x result from not hexagonal SiC but microtwins of 3C-SiC, and twin inclusions are estimated to be around 1%.