| In this study, 138 maize inbred lines are pollinated with flower-net bags during their flowering periods in two consecutive summers in 2016 and 2017 in Taian, and their seed setting rates are studied in comparison with that of natural open-pollinated ones. The infertility caused by filaments is identified by both bagging and natural open pollination, and whether the infertility is caused by pollen. Evaluation on heat resistance of maize inbred lines is established and some heat-resistant maize inbred lines are selected. Based on the seed setting rate of natural open pollination with a daily average temperature more than 30°C for both the two years, the materials are classified into four types. Among them, high heat resistance, moderate heat resistance, relatively low heat resistance and no heat resistance. Regarding the maize inbred lines pollinated with flower-net bags with a daily average temperature more than 30°C, the number of materials with low seed setting rate is 133, the number of materials with low seed setting rate caused by poor heat resistance of filaments and pollen is 68 and 65, respectively. Besides, Five heat-resistant materials were: Jing2416, Bjianba-1-2, B138-1-2, (488/8001-1-4)-2-1-2 and Pr07500-1-1. The results have reference value for breeding and evaluation of heat-resistant inbred lines during flowering and pollination.