OBJECTIVE： To analyze the relevant factors of drug shortage， and to provide reference for improving the availability of drug supply. METHODS： Based on literature study， influential factors related to drug shortage were summarized to designed questionnaire （including 18 influential factors of drug shortage and opening answer）. Stratified cluster sampling was used to collect 6 states and cities in Yunnan province. Questionnaire survey was conducted among relevant persons in charge of production enterprises， circulation enterprises and hospitals. The common factors were collected with principal component analysis. RESULTS & CONCLUSIONS： Totally 550 questionnaires were sent out， and 535 questionnaires were collected， involving 531 valid questionnaires. The principal component analysis extracted 4 common factors which greatly influenced drug shortage. Those factors in descending order of impact degree were price factor， production capacity factor， requirement factor and usage factor （the standard coefficient was 0.54， 0.51， 0.48， 0.47， respectively）. The government is suggested to improve drug price policy and play the function of the supervisor. Medical institutions should improve rational drug use， explore and establish scientific management system of shortage drugs. Production and circulation enterprises should participate in monitoring actively and raise the awareness of rules and awareness of social responsibility.