The plane problem of nonlinear elasticity for bi-material plane with an interface crack is solved. The plane is formed by joining of two half-planes from different materials. Mechanical properties of half-planes are described by the model of semi-linear material. Application of this model has allowed using the methods of theory complex functions in nonlinear problem and to obtain exact analytical solution. The values of nominal stresses and displacements are founded. As an example the case of a free crack in plane subjected to constant nominal stresses at infinity is studied. From the exact solutions the asymptotic of the stresses have been constructed in a vicinity of crack tip and stress intensity factors are calculated.