The ultrafast transient absorption spectroscopy of interband excitation is utilized to evaluate the ultrafast carrier recombination dynamics in the conductive (n-type) nitrogen (N)-doped and semi-insulating (SI) vanadium (V)-doped 6H-SiC wafers. The carrier relaxation of n-type 6H-SiC with carrier lifetime more than 10 ns is dominated by indirect recombination through N impurities and/or inherent defects. Compared with the n-type 6H-SiC, the V-doped one has a pronounced modulation of transient absorption, resulting from an additional carrier recombination process caused by the carrier trapping of V deep levels. The carrier-trapping with a lifetime of about 160 ps is more than two orders of magnitude faster than the indirect recombination. With a simplified energy level model and the global analysis, the carrier recombination mechanism is investigated and the carrier lifetime of 6H-SiC is determined accurately.