In order to explore the optimal visual warning coding form when multiple targets alarm at the same time on the mine gas monitoring interface, the paper adopted three visual coding forms of color, size and character to conducted single target and double target visual search experiments for three alarm levels of attention, warning and danger based on the mine gas monitoring system. Through the analysis of the accuracy, response time and subjective score, the results show that whether it is a single-target or dual-target visual search experiment, the search performance is optimal when the interface adopts the color-coded visual warning form. Compared with character encoding, the search time is shorter with size encoding, but the accuracy is lower. The experimental results also find that in the dual-target visual search experiment, the similarities of alarm levels have significant effect on response time. The response time of two targets with the same alarm level is shorter than that of two targets with different alarm level, and the second target is easier to be found during the search process. The results of this study are of great significance to improve the security of the mine gas monitoring interface and reduce the cognitive decision-making errors of monitoring personnel, and also have certain guiding value for the design of multiple-target visual warning forms in other monitoring interfaces.