The complex Spiraea japonica L. (Rosaceae) includes seven varieties of small foliose shrubs widespread in eastern Asia and used as folk medicines to treat malaria, inflammation and analgesics. To investigate the relationship between its chemical diversity and the physical environmental changes in eastern Asia, a comparative phytochemical study was performed on S. japonica var. fortunei and var. glabra collected in Zhejiang Province, eastern China. Eight kilograms of dried powder of S. japonica var. fortunei and 12 kg of dried powder of S. japonica var. glabra were individually extracted with ethanol by reflux, and the extracts were processed through acid-base extraction, column chromatography (silica gel, Sephadex LH-20, reversed-phase C-18 silica gel) and recrystallization. Two hetisine-type diterpene alkaloids (spiredine and spirasine 3) were obtained from S. japonica var. fortunei, while five hetisine-type diterpenoid alkaloids (spiredine, spirasine 3, spirasine 2, spiradine C and spirasine 5/6) were obtained from S. japonica var. glabra. The results showing all the diterpene alkaloids of these eastern China varieties are hetisine-type provide further support for the hypothesis that the complex S. japonica originated in the southwest of China and showed an evolutionary tendency from west to east.