The Integral transparency P2, which is corrected by the composite transparency coefficient Pm corresponding to the atmosphere mass M=2 (H=90 degree), is defined as the atmospheric transparency index in order to get over the FORBERS effect (namely disturbance to solar spectrum component variations caused by atmosphere mass). Based on the solar radiation data more than 40 years in Urumqi, Kashgar, and the correlative radiation data and meteorological data in Taklimakan desert hinterland and its adjacent regions, the annual, monthly and daily variations of atmosphere transparency P2 are analyzed. Furthermore, the primary meteorological factors influencing P2 are also discussed. The results show that the annual P2 of Urumqi and Kashgar gradually went down in recent 40 years, and the descending trend accelerated from 1990s. The decadal descending trend of P2 is remarkable in winter (January) and spring (April), but slight in summer (July) and autumn (October). The decadal anomalies of P2 in Urumqi and Kashgar are more than 0.2 in January and April, and less than 0.2 in July and October. The P2 of Xinjiang is the best in winter, second in autumn, and worst in spring. But the winter P2 in Urumqi during the recent years rapidly declines, the highest P2 is in autumn; this similar change also appeared in Kashgar. It is implied that atmospheric pollution mainly caused by human activity is resulting in the worse atmospheric transparency condition in urbanization background. The diurnal variation of P2 in Xinjiang is a concave curve: high in the morning and at night, low at the noon; its daily variation relates to weather process. As a result of the land surfaces are mostly covered with desert and Gobi, the important factors influencing the P2 of Xinjiang are dust content and water vapor pressure change; especially the factor of dust content is the most important factor influencing the P2 variation of the Tarim basin. There is a negative correlation between dust content and P2, a positive correlation between vapor pressure and P2.