The yield improvement in dryland wheat has been slow, in part because breeders have focused primarily on higher yields rather than the stability of yield across environments. We apply allometry theory to investigate the underlying mechanisms of the yield and yield stability in multi-sites across 20 years in Gansu and the yield improvement of new cultivars Zhongmai 175 in China North winter wheat areas. Our results indicate that the yield stability has reduced with the progress of solely pursuing yield improvement in recent. Meanwhile, the reproductive allometry exponent is positively correlated with maximum yield (R2 = 0.41, P < 0.05; which is defined as yields under optimal or near-optimal conditions) and variation coefficient of yield (R2 = 0.65, P < 0.001). In addition, the higher yield of Zhongmai 175 was found in all winter wheat areas, compared to local cultivars. The height allometry analysis show height growth was achieved at the cost of grain yield, including grain seed number and size, which can explain the yield advantage of Zhongmai 175 with dwarf traits. The ecological implication of reducing plant height after the “Green Revolution”, is weakening the negative effect of height growth on grain yield. Thus, we conclude here, that allometry theory can provide a novel perspective to understanding the breeding strategies of dryland crops.