As phosphorus ore is produced underground, any breakdown of equipmentes would lead to a halt of production. In order to reduce occurrences of equipmentes breakdown and thus reduce the influence of stoppage on phosphorus ore output, a mathematical model was established based on a deep insight into the production system. The model was used to study the availability and reliability of the production system, the averaged normal operating time, averaged repair time, averaged production cycle and the occurrences of breakdown per unit time under steady conditions. The study shows that phosphorus ore mining enterprises can make their own precautions according their own conclusions drawn from the study.