he effect of complex crystal structures on indexing single crystal SADPs has been investigated on the base of the indexing SADPs of phases in titanium alloys. According to the structure, SADPs can be indexed by one of the following three methods: I .directly indexing SADP by analyzing result according to a Brayals lattice which the structure belongs to; 2.indexing the SADP by using the result gotten according to a suitable Brayals lattice and a necessary mathematical transformation a. indexing the SADP with result calculated with a computer program which was modified according to the diffraction condition of the structure.A pure hkl method in programming for analyzing the corn plex structure is presented to make the programming easier. In the condition of presenting a structure extinction,the SADP can be indexed with the result calculated with present program used foe Brayals lattices and the program modified according to the structure simultaneously. The ideal method for indexingSADPs is a program modified according to the diffraction condition, structure extinction and double d if fraction of a complex structure.