Preparation method for crystalline dibenzothiazepine derivative

The invention discloses a preparation method for a crystalline dibenzothiazepine derivative. The crystalline dibenzothiazepine derivative is synthesized through chlorination reaction, condensation reaction and salt forming reaction by taking dibenzo[b,f][1,4]thiazepine-11-[10H]one as an initial raw material. According to the preparation method, in preparation of 11-chlorine-dibenzo[b,f][1,4]thiazepine, phosphorus oxychloride which is high in toxicity and pollution is replaced by oxalyl chloride which is low in toxicity and pollution; the use of N,N-dimethyl aniline which is high in pollution is prevented, so that the pollution on the environment is greatly reduced; by virtue of salification by crystalline 11-[4-[2-(2-hydroxyl ethoxyl)ethyl]-1-piperazinyl]dibenzo[b,f][1,4]thiazepine free alkali, acquisition of high quality fumarate is ensured, the production cost is effectively lowered, and the batch production is facilitated.