CC1125 issue

You are using a very small modulation factor given 4GFSK. Do you do your tests conducted or radiated? Have you checked to see if you have noise on the air in the band you are doing tests in?

How about MSK?

Mentioned parameters are about MSK...and I'm planning to produce my device as MSK

I test both conducted and  radiated.

At first I was thinking my antenna has problem. but it has just 2~3dB difference in 430~480MHz. It tested in  TEM-CELL(device to device).  

I can't find any difference at conducted one also 

*I've checked my office environment with spectrum analyzer connected antenna. There is no interference.

*I'm selling 900MHz  product (CC1120+CC1190) aslo......but I've never seen this problem.

Please give me advice.

From CC1125 data sheet, page 19. It is expected that there will be degraded sensitivity at multiples of XOSC/2. We recommend that the RF channel is kept RX_BW/2 away from XOSC/2.

Using a 40 MHz TCXO there will be degraded sensitivity at 480 MHz (and 460 and 500 MHz). In your case, with RX filter BW you should avoid frequencies in the range 480 MHz +/-156.25/2 kHz

From your original post I read it as you have issues in the range from 470 to 480 MHz and not just 480 MHz, is this the case?

I'm sorry. Please see 480MHz only.....not 470 to 480.

Simply I just want to use 480MHz  without any degradation.

As Sverre pointed out the sensitivity is degraded at multiples of the clock frequency. If you want optimal performance on 480 MHz you have to use a different crystal frequency than 40 MHz.