COVID-19 is a new type of virus, in its initial period, its infection characteristics can not be completely determined, which cause that its infection scale and development trend can not be accurately estimated, therefore, aiming at the emergency of COVID-19, this paper proposes a inventory model with the smallest total loss under certain service level. Because of the uncertainty of COVID-19 epidemic development trend, the real quantity of its emergency materials can not be determined, therefore, credibility theory is introduced, the real operation of the inventory model established in fuzzy interval by combining the epidemic characteristics is strong. By giving the calculating examples of low cost emergency supplies and high cost emergency supplies, by using MATLAB software to calculate the corresponding results and to analyze the data and the graphics, the optimal ordering strategy with the minimum total loss when considering the service level can be obtained. The special emergency of COVID-19 causes the demand unable to completely copy the experience of the predecessors to set up material inventory, however, the fuzzy number is a rough range, as a result, the expectation of high efficiency and low loss can be achieved under the narrowing of the demand range as much as possible, the emergency material inventory can be better managed.