Aims: Biological pacemaker (bio-pacemaker) experiments showed that the expression of connexin – Cx43 was suppressed in biological pacemakers. Decreased Cx43 inhibited electrical coupling between bio-pacemakers and adjacent cardiac cells, which can maintain the synchronous pacing behavior of bio-pacemaker. At the same time, moderate Cx43 is necessary to encourage autonomous electrical signal being propagated to cardiac tissue. In this paper, we quantify the influence of coupling between pacemakers (PMs) and ventricular myocytes (VMs) on signal propagation based on a cardiac slice model. Our study may explain the electrical propagation mode of bio-pacemaker. Methods: VMs model was cited from TNNP06 model, while PMs model was constructed according to our previous work. A cardiac tissue model was designed as PMs connecting with VMs. We manipulated the diffusion coefficient (D) to simulate Cx43 suppression. Results: When the D between PMs and VMs was original value, the PMs tissue could produce synchronous pacing behavior but autonomous signal could not be propagated to VMs. Only if D was suppressed by more than 70%, can PMs tissue drive the whole cardiac tissue. Conclusion: Electrical coupling between PMs and VMs decides if automatic pacemaking signals can drive adjacent cardiac cells.