The optimal temperature in favor of aflatoxin contamination in peanuts would rise along with the decrease of the latitude. Among the 2494 peanut samples in the four provinces, the percentages of aflatoxin-positive samples and mean contents of aflatoxins and the percentages of non-compliant samples were highest in Sichuan and lowest in Liaoning. The aflatoxin B1 content in peanuts at harvest was closely related to climatic conditions before harvest. When the mean temperature was close to 23 ◦C, minimum temperature was close to 20 ◦C, and maximum temperature was close to 29 ◦C under drought stress, the level of aflatoxin contamination was high. When the mean temperature was 15-28 ◦C, minimum temperature was 13-26 ◦C, and maximum temperature was 20-33 ◦C under drought stress, the content of aflatoxin B1 would go beyond the limit of 20 mg/kg.