Objective:To observe the feature of Lorenz plots of dual parasystole ,and explore its differential diagnosis significance .Methods :Lorenz plot data of seven patients diagnosed as dual parasystole was retrospectively analyzed . They were compared with those of single source premature beat ,dual premature beat and single source parasystole . Results :All case data were divided into six groups (seven cases in each group) ,its features were :group 1 [ (single source atrial premature beat (APB)] ,plots were characterized with three distribution and sinus rhythm located on 45° line ;group 2 (dual source APB) were five distribution with the same sinus rhythm location ,the points set before and after premature were located on its two sides ,the plot was symmetry ,slopes of line B were within 0~1 in group 1 and 2 and its slopes were no significant difference (P>0.05);group 3 was single source ventricular premature beat (VPB) ,show four distribution pattern ,sinus rhythm was located on 45° line ,the points set before and after prema-ture were almost parallel to X and Y axis ;group 4 ( dual source VPB) were in six distribution with the same sinus rhythm location ,its difference with single source VPB was the points set before and after premature were symme-try;slopes of line B all trends to 0 in group 3 and 4 ,their slope also no significant difference (P>0.05);Group 5 (single source parasystole ) was characterized as four distribution vertical to 45° line ,premature point set was vertical to 45° line ,point set before and after premature were vertical to axis X and Y respectively ;group 6 (dual parasysto-le) were seven distribution vertical to 45° line ,were similar to that of single source parasystole ,the difference was figure of group 6 was dual distribution ;slopes of line B were close to ∞ in group 5 and 6 ,and its difference were no significant (P>0.05) .The line B slopes in group 5 and 6 were significantly higher than those of group 1&2 [ (∞ ) vs .(4.78 ± 0.19)] ,and those of group 1&2 were significantly higher than those of group 3&4 (0.36 ± 0.06) ,P<0.01 all .Conclusion:There are significant difference in Lorenz plot features among single (dual) source atrial/ven-tricular premature beats ,single source parasystole and dual parasystole .Lorenz plot is helpful to differential diagno-sis of parasystole .