This paper is aimed to introduce the definition and application of Population Impact Measures (PIMs). The PIMs use Number Need to Treat (NNT) for reference and generalize the variables of clinical research to interest population, which then can be used to measure the effectiveness of interventions and the harmfulness of risk factors, so as to provide evidence for making public health policy. Of the PIMs, the variables used for measuring the effectiveness of interventions include Disease Impact Number (DIN), Population Impact Number (PIN) and Number of Events Prevented in your Population (NEPP); The variables used for measuring the harmfulness of risk factors include Exposure Impact Number (EIN), Exposed Cases Impact Number (ECIN), Population Impact Number (PIN), Case Impact Number (CIN) and Population Impact Number of Eliminating a Risk factor (PIN-ER-t).