Competitive oxidation of Al and Ti and the modification of inclusions in steel have been studied by aluminium deoxidation and calcium treatment test of 0. 007% -0. 015%C- 15.96% ~ 16. 94% Cr- 0. 08% ~0. 36%Ti- 0. 015% ~ 0.124% Al ferrite stainless steel liquid in a 500 kg vacuum induction furnace and relative thermadynamics calculation. Results show that as [Ti

]

/[Al

]

is less than 2. 50

the main oxide inclusions are A1

2

O

3

with increasing [Ti

]

/[Al

]

the main inclusions in steel change to MgO-Al

2

O

3

-TiO

x

and A1

2

O

3

-TiO

x

from Al

2

O

3

and the average dimension of inclusions gradually decreases； after calcium treatment with incre

asing [Ca

]

/[Al

]

(0. 01 -0. 08)

the amount of compound inclusions containing calcium in steel increases; the compound inclusion consists of oxide core and TiN or Ti(CN) periphery.