Abstract: Civitas Pre-M1xed (referred to as Civitas) is a food-grade synthetic isoparaffin emulsifier compound produced by Petro-Canada. The safety of Civitas was evaluated using seed germination and pot experiments in this study. At the same time, the sensitivity of Alternaria alternata isolated from tobacco to Civitas and the effects of Civitas on tobacco brown spot disease were determined using mycelial growth rate and potting methods. The seed germination rate of the control was 82.7%. After treated by 5% and 10% aqueous solution of Civitas, the seed germination rates decreased to 58.3% and 32.1%, respectively, while 1% and 0.1% of Civitas had no significant inhibitory effect on seed germination. 20% and 10% aqueous solution of Civitas had a certain inhibitory effect on the plant height and stem circumference in the rosette stage. However, 5% and 1% aqueous solution of Civitas had no such effect. None of the tested aqueous solutions of Civitas had inhibitory effect on the growth of the plant height in the bud stage, but 20% and 10% aqueous solution of Civitas had a certain inhibitory effect on the stem growth during this stage. In addition, the aqueous solutions of different volume fraction of Civitas showed a certain degree of inhibitory activity againstA. alternata, and the inhibitory effect which was improved with the increase of volume fraction. When the volume fraction of Civitas solution was 20%, the inhibition rate was 54.1%. Civitas exhibited curative and preventive effects against tobacco brown spot disease 10 days after foliar spray treatment with 5% Civitas, disease of tobacco caused byA. alternatawas reduced by 59.3% in preventive trials, and by 19.6% in curative trials. The results have provided reference and basis for the further safety evaluation of Civitas and its potential applications.