The samples in this paper were synthesized by high temperature solid state reaction technique. The luminescence of the 4f5d states of Pr

3+

doped in Sr

2

SiO

4

and the characteristics of the energy transfer from Pr

3+

to Gd

3+

have been studied. In Sr

2

SiO

4

the energy level of the lowest 4f5d band of the Pr

3+

located at about 36000cm

-1

which was much lower than that of the free ions

and was below the

1

S

0

energy level of the 4f

2

configuration

so when excited into the 4f5d band

there was possibility to get the radiation transition of the 4f5d states. The energy gap between the lowest 4f5d band and the

3

P

2

level was about 14000cm

-1

which was big enough that the non radiation from the 4f5d band to

3

P

2

level was so small

the radiation transitions from

3

P

0

and

1

D

2

level was unobserved

which indicated that the efficiencies of the 4f5d→4f radiative transition was high. From 0mol to 0.01mol of Pr

3+

in Sr

2

SiO

4

the emission strength became stronger with increasing the Pr

3+

concentration. From 0.01mol to 0.03mol

the emission strength was almost constant

which was due to the concentration quenching of Pr

3+

in Sr

2

SiO

4

. When excited by 240nm

the emission spectrum of Pr

3+

was consisted of three bands

which was from 260nm to 440nm

the three peaks were at about 276

318 and 396nm which corresponded to the radiation transition from the lowest 4f5d band to

3

H

4

3

H

6

and

1

G

4

respectively. The excitation spectrum was from 200nm to 260nm

when employed Gaussian fit

three bands could be got

the peaks were at about 218

240 and 250nm

respectively. In Sr

2

SiO

4

Pr

Gd

when excited by 240nm

the 311nm emission of Gd

3+

was observed which could not be got in Sr

2

SiO

4

:Gd

the energy transfer from Pr

3+

to Gd

3+

happened. There were overlap between the transition of the 4f5d states to 3H 4 of Pr

3+

and the absorptive transition of the Gd

3+

8

S

2/7

→

6

I

so the

6

I levels took part in the energy transfer process. Because the oscillator strength of the

6

I levels was 10～20 times stronger than that of the

6

P levels

the energy transfer from Pr

3+

to Gd

3+

was more efficient than that of only the Gd

3+

6P levels was included in the energy transfer process. When the concentration of Pr

3+

was constant

the Pr

3+

emission strength became weaker and the Gd

3+

emission strength became stronger with increasing the Gd

3+

concentration. When the Gd

3+

concentration is bigger than 0.07mol

the concentration quenching happened and the Gd

3+

emission strength decreased with increasing the Gd

3+

concentration.