[Objective] Under the wave of digital transformation in various sectors， the data center industry is booming and showing a new trend of clustering and wide-area interconnection. Given the high energy consumption and high carbon emissions that are common in data centers， this paper aims to guide them to actively participate in the low-carbon dispatching of the power grid based on the spatio-temporal flexibility of their computing loads， in order to achieve the goals of energy conservation， carbon reduction， and economic operation for both data centers and the power grid. [Methods] This paper proposes a high-precision dynamic carbon emission accounting method， which takes into account the spatio-temporal differences in network losses and carbon emissions. It accurately calculates the key "nodal carbon potential" signal through a power iteration traceability algorithm and， based on this signal， proposes a coordinated two-layer dispatching model for interconnected data centers and the power grid， where the upper-layer model aims to minimize the operation cost， carbon emissions， and renewable energy curtailment， while the lower-layer model aims to minimize the integrated electricity-carbon cost. The dispatching model interacts and iterates through the carbon potential and load adjustment signals between the upper and lower layers to find the optimal dispatching strategy for the system. [Results] The case study based on the improved IEEE 39-bus system shows that under the proposed coordinated dispatching strategy， data centers actively transfer online loads to low-carbon potential nodes for processing during high-carbon potential periods and delay the processing of local offline loads. During low-carbon potential periods， they take on more online loads and concentrate on processing previously delayed offline loads， achieving significant energy conservation and carbon reduction effects. [Conclusions] The two-layer optimization model proposed in this paper can effectively guide data centers to achieve economic and low-carbon coordination， providing a new technical tool for the green transition of data centers and the low-carbon dispatching of the power grid.