Abstract: In order to provide the basis for industrial & agricultural production and permafrost research, analyze the permafrost duration, variation characteristics at maximum depth of permafrost and response to climate warming in semi-arid region of western Liaoning based on winter climate data from 1960/1961 to 2009/2010. The results showed that: permafrost duration in the western Liaoning was obviously impacted by climate warming, the temperature tendency was 0.787℃/10 a, nearly 10 a, 3.2℃ higher than the 1960s. Under the warming environment, permafrost frozen period changed smoothly; the permafrost melting date was being ahead of time, nearly 10 a, 7 d earlier than in the 1960s; the permafrost duration was decreasing, but not obvious; permafrost maximum depth was significantly decreasing, the temperature tendency was -4.120 cm/10 a, nearly 10 a, 12 cm less than the 1960s. Air temperature, ground temperature and precipitation made the significant impact on permafrost maximum depth, there was a linear relationship between air temperature and permafrost maximum depth, when the temperature increased by 1°C, the maximum depth of permafrost would decrease by 5.74 cm. The shallowing permafrost was conducive to industrial & agricultural production, and however, it caused pest overwintering and northward movement of plague boundaries, resulting in unfavorable impact on pest control and epidemic prevention.