In order to take into account the low-carbon emission, economy and safety in the whole life cycle in structural design, it is very important to quantify the impact of low-carbon incremental cost on optimization decision-making. This paper proposes the concept of low-carbon incremental cost in the whole life cycle, that is, the additional cost caused by reducing carbon emissions in the whole life cycle, and constructs a structural reliability and cost optimization model that integrates low-carbon constraints. Based on this model, the influence of the variation coefficient and probability distribution type of load and resistance on the optimization results is quantitatively analyzed. The results show that the increase of the coefficient of variation will significantly improve the optimal safety factor, but at the same time reduce the optimal reliability index; the influence of probability distribution type is relatively weak. Taking the reinforced concrete frame structure apartment building as the research object, the recommended value of the annual optimal target reliability index of this kind of structure under the combination of various failure consequence levels (slight, medium and serious) and safety measures cost levels (high, medium and low) is determined. Compared with the traditional standard values, the recommended values of this series differ from 0.02 to 0.23, which can provide quantitative decision-making basis for promoting the collaborative optimization design of low-carbon buildings in terms of reliability, economy and sustainability.