We hope to understand the driving force for peptide assembly, especially the disease related amyloid aggregation.In this work, the assembly stability of model peptides (e.g.H5F5、 F5H5、 H5A5、 A5H5、 A5N5、 N5A5、 F5N5、 N5F5) with different side chains has also been observed with STM(Scanning Tunneling Microscopy).The different length distributions reveal the sequence effects on peptide assembly and the assembly stability follows the order of F > N > A > H.These works may provide new insights for understanding the structure of amyloid aggregates, the aggregation process and mechanism for inhibiting the amyloid aggregation.