The invention discloses a method for monitoring horizontal well staged fracturing effects by a micro-element tracer. The method mainly includes the steps: 1) selecting a micro-element with low background concentration as the tracer; 2) estimating the dosage of the tracer at each stage according to the dosage of fracturing fluid at each stage; 3) adding the tracers into a fracturing blender truck by a constant-flow pump through a ground low-pressure pipeline, and adding different tracers into different layer stages in fracturing; 4) performing cluster sampling on fracturing flow-back fluid after fracturing, detecting concentration of the tracer in the flow-back fluid, drawing a curve of the concentration of the tracer along with time variation, calculating water yield of each stage, analyzing fracture morphology after each stage is fractured, determining contribution of each stage to the water yield, and defining connectivity between a well bore and a well after fracturing. The method solves the problems that signal-to-noise ratio is low, reliability is poor, cost is high, radioactive contamination is generated, and the fracturing effects of each stage cannot be accurately evaluatedafter horizontal well staged fracturing is implemented.