Objective To investigate the changes of hepatic function before and after transcatheter arterial chemoembolization (TACE) in primary liver cancer patients with different quantifications and classifications using 13C-methacetin breath test (13C-MBT), and to provide risk predicts for TACE. Methods 28 cases of primary liver cancer patients and 10 cases of metastatic liver cancer patients were selected.General examination items of liver function and 13C-MBT detection were performed on all cases. Primary liver cancer was divided into 4 groups according to the results of 13C-MBT (group 1 was normal or pathological liver damage; group 2 was grade A; Group 3 was grade B; group 4 was grade C). 13C-MBT detection was carried out in week 1 and 4 after TACE. Results The three parameters of 13C-MBT is 13CO2 maximum excretion rate before 40 min/27 (MVmax40), 13CO2 cumulative excretion of 40 min/12 (CUM40), and than of 120 min/28(CUM120). Compared with the parameters [(0.628±0.191)%, (0.628±0.289)%, (0.577±0.286)%] before TACE in hepatic metastasis, there were no statistic effect between week 1 [(0.600±0.187)%, (0.559±0.189)%, 0.587±0.181)%] and week 4 [(0.700±0.230)%, (0.734±0.229)%, (0.724±0.252)%] after TACE. Conclusion The lower classification of 13C-MBT, the more impairment to liver function after TACE. This could provide an important diagnostic basis for TACE.