In this paper, deals with how to design an MSHE in the context of cryogenic applications. Traditional method based on composite curves is unable todesign an MSHE in cryogenic applications due to the nonlinear variation in heat capacity-flowrates when a stream changes phase while exchanging heat.Using a new proposed method in this paper to design an MSHE and applying this method in Hysys through building an extension unit operation,design of an MSHE in cryogenic processes is provided. Real geometry specifications of coldbox and operating conditions of flowing streams in Ethanerecovery unit at South Pars Gas complex of Iran, have been compared with the values obtained using the proposed method, such that the results in thispaper indicate the new method is a proper method to design of MSHE in cryogenic units. MSHE dimension and weigth calculated have a goodagreement with real size.