A supported TiCl

4

/MgCl

2

catalyst without internal electron donor (O-cat) was prepared firstly. Then it was modified by 2

6-diisopropylphenol to make a novel modified catalyst (M-cat). These two catalysts were used to catalyze ethylene/1-hexene copolymerization and 1-hexene homopolymerization. The influence of cocatalyst and hydrogen on the catalytic behavior of these two catalysts was investigated. In ethylene/1-hexene copolymerization

the introduction of 2

6-

i

Pr

2

C

6

H

3

O- groups did not deactivate the supported TiCl

4

/MgCl

2

catalyst. Although the 1-hexene incorporation in ethylene/1- hexene copolymer prepared by M-cat was lower than that prepared by O-cat

the composition distribution of the former was narrower than that of the latter. Methylaluminoxane (MAO) was a more effective activator for M-cat than triisobutylaluminium (TIBA). MAO led to higher yield and more uniform chain structure. In 1-hexene homopolymerization

the presence of 2

6-

i

Pr

2

C

6

H

3

O- groups lowered the propagation rate constants. Two types of active centers with a chemically bonded 2

6-

i

Pr

2

C

6

H

3

O- group were proposed to explain the observed phenomena in M-cat.