The Tangshan Sipingtou (TSSPT) germplasm in inbreds of the Tangshan Sipingtou heterotic group ofmaize in China was mainly derived from Huangzao4, and the source of TSSPT germplasm was severely restricted by theinbred Tangsipingtou. Except Tangsipingtou, the contents of TSSPT germplasm were only 50 % or less in inbreds ofthis group, with the existence of more than 20 non-TSSPT germplasms which resulted in abundant genetic diversity inthis group. 95. 12% inbreds of this group contained both TSSPT and UNS(unknown source) germplasms in the ratio of1: 1, with 12.5 -50% of each germplasm. The recombination of TSSPT and UNS germplasms had producedHuangzao4, the most important maize germplasm of compact plant form. About 90. 24% of the inbreds inthis group were the inbred Huangzao4 and its derivatives. 11.11% of the derivatives contained 25 - 50% ofLuda Honggu(LDHG) germplasm, and 16.67% of the derivatives contained 12.5 - 25% Creole and 6.25 -28.13% LSC germplasms. In addition, 97. 56% of the inbreds of this group contained one or more non-TSSPT germplasms. This indicates that the germplasm base of inbreds of the TSSPT heterotic group hadchanged and evolved away from actual TSSPT germplasm.