Disclosed is an automated platelet analyser, comprising a sampling cup, a preparation cup, an analytical cup, a pipette, a syringe for blood sampling, a polymerization inducing agent syringe, an analytical liquid syringe, and a device for uniformly mixing blood samples. Also disclosed is a method for analyzing platelets, comprising the following steps: step 1, drawing the blood sample to be analyzed, and adding it to the sampling cup step 2, drawing the blood sample in the sampling cup and adding it into the preparation cup step 3, adding an analytical liquid into the preparation cup for the first quantitative dilution step 4, drawing the blood sample in the preparation cup in a pre-determined quantity, and adding it into the analytical cup step 5, adding the analytical liquid into the analytical cup for a second quantitative dilution step 6, detecting the original platelet count of the blood sample in the analytical cup step 7, adding the polymerization inducing agent into the sampling cup step 8, repeating step 2 to step 5 at specified time intervals to detect the platelet count of the blood sample in the analytical cup at each time point after the polymerization inducing agent is added step 9, obtaining the aggregation rate of platelets.