The selective seed abortion (SSA) universally exists in angiosperm plants. It is helpful to understand the formation mechanism of SSA and various reproductive strategies for analyzing the seed setting pattern and its influencing factors. To explore the pattern of SSA and related influencing factors, we carried out studies on pollination process, dynamics of ovule development and resource allocation in Caragana acanthophylla. The results showed that:(1) Caragana acanthophylla had a mating system of obligate outcrossing due to the highly self-incompatibility, in which the main pollinators were bees with a general pollination system. There were no pollination limitations in the pollen source and pollination intensity with a natural fruit setting of (86.00±4.96)%. But there were significant timing effects in fertilization. (2) Caragana acanthophylla had (14.00±0.14) ovules per flower, and individual flower remained open for 4-5 days. Seed development started from the top of the pod, and the ovules at the top the of pod began to expand on the 3rd day after flowering. On the 11th day, most of ovules were enlarged. At the same time, those ovules at the base of the pod become aborted, and then ovules fertilized at the top of the pod were aborted. Finally, only 2-3 seeds were formed in the middle of the pod. It was a seed setting pattern of selective abortion type in Caragana acanthophylla, in which ovules in the middle of the pod were matured preferentially and ovules at the top and base of the pod were aborted firstly. (3) The flowering plants in the population had a patchy distribution, in which some plants had many flowers, while others had a few flowers due to the influence of microtopography. Seed setting rate was significantly increased when the resources were regulated by applying water and fertilizer for a few flowering plants. It indicated that there were resource limitations in the process of seed formation. In conclusion, the seed setting pattern was determined by resource allocation of two reciprocal gradients:fertilization order and resource limitations in Caragana acanthophylla, in which the time gradient of fertilization led to the first abortion of ovulesat the basal, while the position effect of resource allocation led to the abortion of ovules fertilized at the top of the pod. The middle ovules had a better development due to the location of intersection of two resources transportation, in which it was a tradeoff of fertilization time and location effect of resource allocation.