The structural and elastic properties of some alkaline earth mono-selenides (AESe : AE = Ca, Sr, Ba) under pressure have been investigated using a two body inter ionic potential approach with modified ionic charge (Zme). This method has been found quite satisfactory in case of the rare earth compounds. The equation of state curve, structural phase transition pressure from NaCl (B1) to CsCl (B2) phase and associated volume collapse at transition pressure of alkaline earth selenides (AESe) obtained from this approach, so have been compared with experimentally measured data reveal good agreement. We have also investigated bulk modulus, second (C11, C12 & C44) and third order (C111, C112, C123 etc.) elastic constants and pressure derivatives of second order elastic constants at ambient pressure which shows predominantly ionic nature of these compounds. First time, we have calculated the Poisson ratio, Young and Shear modulus of these compounds.