SAPO-20 molecular sieve with the SOD framework was successfully synthesized using SAPO-34 as the precursor and isopropylamine (IPA) as the template by phase-transformation route. The influence of post-treatment time (in IPA, H₂O, and SAPO-34 system) and NaOH concentration (in IPA, NaOH, H₂O, and SAPO-34 system) on the products was investigated. The results showed that sheet debris SAPO-34 building the hollow-inside cubic morphologies which was padding with irregular SAPO-34. It was received for the as-synthesized spherical aggregation SAPO-20 with hexagonal shape when the ratio of n(OH^-)/n (H₂O) is 0.12 and the ratio of n(IPA)/n (H₂O) is 0.07 in the synthesis gel. This method not only develops a new route for the synthesis of SAPO-20 molecular sieve, but also provides a way of using waste SAPO-34 catalyst, which can be used as a new exploration model for energy saving, consumption reduction and comprehensive utilization in SAPO-34 catalyst process.