Objective To investigate the effect and safety of thoracic drainage by central venous catheter in critical patients with pleural effusion. Methods A prospective study was carried out,in which 46 critical patients with pleural effusion admitted to department of critical care medicine were included,and according to the types of their primary diseases to make matched pairs,and they were divided into two groups:conventional drainage control group and central venous catheter drainage observation group(each 23 cases). The drainage effect and complications were compared between the two groups,acute physiology and chronic health evaluation Ⅱ(APACHEⅡ)score, quantitative pleural effusion and the counts of white blood cells(WBC)and of platelets(PLT),the levels of prothrombin time(PT),procalcitonin(PCT)and C-reactive protein(CRP),etc. were measured on the baseline and 24 hours after the operation. Results There were no significant differences in the APACHEⅡ score,quantitative pleural effusion,amount and duration of drainage,as well as the levels of WBC,PLT,PT and PCT between group control and observation(all P>0.05). The post-drainage CRP(μg/L)level in group observation was much lower than that in group control(77.26±67.20 vs. 106.13±66.23,P<0.01). There was a trend that the incidence of complication in group control was higher than that in group observation(26.1%vs. 4.3%),but the difference was not statistically significant(P>0.05). Conclusions In the comparison between the conventional drainage and thoracic drainage with central venous catheter,the therapeutic effects for treatment of critical patients with pleural effusion were similar, but the stress was milder and the incidence of complications was lower in the latter group. Therefore,the thoracic drainage with central venous catheter is a safe,effective and alternative method to substitute the conventional drainage for critical patients with pleural effusion.