Determination of methylene blue concentrations of hydrogen sulfide in the air is sensitive and rapid ect. However, the standard curve tend to appear low line slope, leading to measurement errors. In the preparation of ZnS colloidal process, it is nitrogen as the carrier gas and protective gas. Its direct impact on the ventilation conditions colloidal particle size and uniformity of the precision for the calibration concentration have the significant impact, particles size appropriate uniform colloidal solution and the concentration can be more stable and accurate calibration by the standard curve. It was drawn to meet the requirement that is possible, too large or too small particles on the experimental results will lead to a greater impact. This article is related to the verification experiment of nitrogen ventilation conditions (uniform or not) with aeration velocity on the slope of the curve standard. The experiment we have come to: In this study, ZnS colloidal preparation on passing the nitrogen should be uniform, and the ventilation rate is smaller and needed to continuously bubbling one by one, in which the case of the experimental results, it is required by the standard curve that is drawn 0.1489, spiked recovery rate of 97.5% and 99.0%.