The present invention relates to a process for preparing polyurethane sheet/laminate with reduced bubbles, comprising the steps of applying a polyurethane system obtained by mixing an isocyanate component (A) and a polyol composition component (B) to form a base coat layer, wherein the components (A) and (B) are kept saperately in tanks under vacuum before mixing and the application of the polyurethane system is implemented via knife coating under relative humidity of 65% or below. The present invention further relates to a polyurethane sheet/laminate prepared by the described process and synthetic leather made from the polyurethane sheet/laminate.