The high mixing uniformity for pesticides and carrier water was an important requirement in direct nozzle injection system (DNIS) used to alleviate the waste of pesticides and protect environment from being contaminated by pesticides residues. To evaluate the mixing effects of pesticides mixers, new analysis methods for mixing uniformity were presented and the swirling jet mixer was used to carry out the experiments of in-line mixing for the water and non-water soluble pesticides under variable working conditions. Quantitative descriptions for mixing uniformity of mixture inside the mixer were achieved based on calculating the coefficient of variation(α) and areaweighted uniformity index (γ) for the regions of interest（ROI） in the mixture images of the mixer. The accuracy of the analysis methods was verified by comparing the images of artificial premixed mixture and the images of unmixed mixture, as well as the images of mixture in standing state, and it proved that the indexes could be taken as criteria to judge whether the mixers could meet the requirements for in-line mixing or not. The experiments result under variable working conditions revealed that the mixing uniformity was increased with higher carrier flow rate and the flow rate of 2400mL/min gave rise to the best uniformity while the uniformity was declined heavily with lower flow rate under the conditions of settled mixing ratios. When the carrier flow rate was remained unchanged, higher mixing ratios would contribute to higher uniformity. Therefore, it was necessary to provide high flow rate to ensure good mixing uniformity when it came to lower mixing ratios. Normally, The criteria of α=0.2239 and γ=80.39% were set to be the thresholds for uniform mixtures and non-uniform mixtures as there were no non-scatted pesticides remaining in the mixer when the indexes were better than them. Moreover, the filtering results showed that the flow rate which was higher than 2000mL/min could meet the uniformity requirements at different mixing ratios while the flow rate of 800mL/min could not meet the uniformity requirements at any mixing ratios, and the mixing uniformity at part of these ratios could be satisfied when the flow rates were between 800mL/min and 2000mL/min.