The invention discloses a method for calculating accidental E-layer short wave field strength of a mid-latitude region. The method includes the following steps that A, according to position information of a receiving and transmitting point, a great circle distance and a reflecting point position of a short wave link and the electronic cyclotron frequency of the short wave link are calculated, anda radio wave radiation elevation is calculated based on the equivalent theorem; B, depending on a radio wave environment observation station of the science and technology industry of national defense,an ionized layer vertical sounding diagram and an ionized layer inclined sounding diagram of the reflecting point position are obtained; C, if there are no ionized layers foE and foEs which can be directly observed at the reflecting point position, firstly, an MUFEs value of inclined sounding is converted into an foEs value at a middle point of an inclined sounding link; D, according to short wave communication features, occurrence conditions of strong Es are determined, the ionized layer absorption loss of the reflecting point position is calculated, and accordingly the accidental E-layer field strength is worked out. According to method for calculating the accidental E-layer short wave field strength of the mid-latitude region, ionized layer vertical sounding and inclined sounding datacan be comprehensively utilized, and the foEs value of the reflecting point position is worked out.