Abstract: Clarifying the rights and responsibilities of carbon emissions and establishing a theory and method system for carbon flow distribution in net-zero carbon evolution serve as the foundation for low-carbon transformation and development in the power system.. Existing methods of carbon flow analysis focus on the share of load carbon emission responsibility. This paper proposes a discrete analysis theory and calculation method of carbon flow distribution in power system with spatiotemporal coupling from the perspective of the consumption contribution of load to renewable energy. First, aiming at improving the consistency of time series characteristics between power supply and load, and consumption of renewable energy, the carbon emission is extended from continuous allocation of single time section to comprehensive evaluation of multiple continuous time sections, and a discrete analysis theory is established to analyze carbon flow distribution with multi-period, process-oriented and real-time evaluation. Then, considering the time-space coupling characteristics of power supply and load in the period, a carbon emission evaluation scheme considering the contribution of renewable energy consumption is proposed. Finally, a discrete calculation model of carbon emission flow distribution is established based on the evaluation scheme, and a decoupled calculation method of power flow and carbon emission flow is proposed to achieve efficient traceability of carbon emissions and fast solution of branch/node carbon flow rate. Case study shows that the discrete distribution method proposed can achieve carbon balance of the whole and all links, which proves the feasibility of the theory. In addition, comparing with the existing methods, load nodes can achieve emission reduction without reducing the total power consumption by adjusting the load time sequence, which is conducive to forcing the consumption of renewable energy through carbon constraints. As a result, rationality and superiority of the proposed theory are verified.