Abstract: Drought is one of the main factors restricting agricultural development and food security in China. Identifying agricultural drought accurately and assessing the impact of drought on crop yield in detail is the core of drought research. The results of this research can provide a theoretical basis for drought disaster prevention and mitigation. The water deficit anomaly index of spring maize across the entire growth period was calculated based on daily weather data from 52 meteorological stations in Liaoning Province from 1961 to 2015, and a new drought index for spring maize over the entire growth period was constructed by using Run Theory. Drought yield loss assessment models at the county or city scales were further constructed based on the drought index and yield loss rate from 1981 to 2015. Finally, key prevention areas for spring maize drought in Liaoning Province were identified. The drought index for spring maize in Liaoning Province exhibited a decreasing distribution from west to east. The likelihood of severe drought events was higher and the interannual variability of spring maize yield was largest in western Liaoning. The rate of yield loss of spring maize had a significant positive linear correlation with the drought index in more than 80% of the counties in the spring maize main producing area, except for most parts of eastern Liaoning and some counties in central Liaoning. Moreover, significant spatial differences were observed in the yield loss of spring maize. With the same drought index, the region with the largest yield loss rate of Liaoning Province was Chaoyang, followed by the southern and northern parts of Liaoning; the Liaodong Bay and the central plain had the lowest yield loss rate. However, in Fengcheng City and Donggang City, where spring maize growth was not restricted by precipitation, the yield of corn was higher in the years with less precipitation. The results of the present study indicated that the government should pay more attention to drought-sensitive zones such as the Chaoyang District, and northern and southern Liaoning west, and north of the Qianshan Mountains. To increase and stabilize spring maize yield in the above areas, it is necessary to increase drought-tolerant varieties, develop water-saving irrigation, and improve water use efficiency. Most counties in eastern Liaoning and some counties in central Liaoning with abundant rainfall or good irrigation conditions can increase spring maize production by improving planting and management methods. Additional attention should be paid to the prevention of damage caused by floods and cold, especially in Fengcheng and Donggang.