In this paper, we have analyzed the effects of split power/ground plane on high-speed digital printed circuit board experimentally and numerically. Firstly, we have proposed equivalent circuit model of the signal traces, when the signal traces crosses the ground slot. Previously, when modeling a signal trace crossing a ground slot, the ground slot has been modeled as a simple inductor or inductor-capacitor usually. But the new proposed model is based on a slot transmission line model. The proposed model is more intuitive and gives more accurate results for both reflection and crosstalk simulation. Next, we have proposed some slot shapes to reduce the crosstalk and EMI including multi-layer structures. The crosstalk and EMI of the structures were simulated through the method of moments (MOM). Considering the isolation property, we found the best design of all proposed structure is strip line structure with tapered ground slot.