A short-prevented lead frame and a method for fabricating a semiconductor package with the lead frame are proposed, wherein each lead of the lead frame is formed with a thickness-reduced portion at a peripheral position of the lead frame, allowing thickness-reduced portions of adjacent leads to be arranged in a stagger manner. This stagger arrangement significantly increases pitches between the neighboring thickness-reduced portions of leads. Therefore, during a singulation process as to cut through the leads, lead bridging and short-circuiting between adjacent leads caused by cut-side burrs can be prevented from occurrence, whereby singulation quality and product yield and reliability are effectively improved.