The invention provides a method for calculating triangular resistance load of a shield tunnel in a compound stratum. Triangular resistance deformation delta is regarded as superposition of horizontal deformation U(q<1>, q, e<1>, e<2>, g, q) caused by load, except triangular resistance, and horizontal deformation U(kdelta) caused by triangular resistance load PP; taylor expansion of the horizontal deformation U(kdelta) caused by triangular resistance load PP is carried out; furthermore, an expression of the horizontal deformation U(kdelta) obtained by ignoring the higher order term is substituted into a superposition horizontal deformation expression; with the help of numerical values locally, a semi-analytical formula of triangular resistance deformation is solved; and thus, a formula of the triangular resistance deformation delta is obtained. The problem that the traditional shield tunnel triangular resistance displacement calculation formula is not suitable for the compound stratum is really solved; a relatively universal calculation method is provided; and simultaneously, the basis is provided for precisely solving the internal force of a segment of the shield tunnel.