  We uncover the relationship of topology and disorder in a one-dimensional
Su-Schrieffer-Heeger chain subjected to a slowly varying quasi-periodic
modulation. By numerically calculating the disorder-averaged winding number and
analytically studying the localization length of the zero modes, we obtain the
topological phase diagram, which implies that the topological Anderson
insulator (TAI) can be induced by a slowly varying quasi-periodic modulation.
Moreover, unlike the localization properties in the TAI phase caused by random
disorder, mobility edges can enter into the TAI region identified by the
fractal dimension, the inverse participation ratio, and the spatial
distributions of the wave functions, the boundaries of which coincide with our
analytical results.
