Purpose: For anaplastic lymphoma kinase (ALK) gene detection, the centrifugal sedimentation method (CSM) and cell block method (CBM) are commonly used to process samples of bloody pleural effusions (BPEs). However, in practice, the impurity content in the processed samples often affects the results and even leads to the detection failure. The purpose of this study was to establish a cell enrichment method (CEM) by using a disposable membrane cell collector to remove blood and inflammatory cells and enrich lung adenocarcinoma cells in BPE for more efficient RNA extraction and ALK gene detection. Materials and Methods: CEM proposed in this study and the traditional CSM and CBM were used to treat BPE samples collected from 37 lung adenocarcinoma patients. A DeNovix DS-11 ultraviolet spectrophotometer was used to measure the concentration and purity of extracted RNA. Amplification refractory mutation systems (ARMS) and ABI 7500 fluorescence qPCR were used to detect ALK gene. Through statistical analysis, the CEM was compared with the CSM and CBM in RNA concentration, purity, and ALK gene detection results. Results: The concentration of RNA extracted by using the CEM was significantly higher than that extracted by using the CBM and CSM (p < 0.001). The purity of RNA extracted by using the CEM was significantly higher than that by the other 2 methods (p = 0.011, p = 0.005). ALK gene testing with PCR was successful in all the samples using the CEM, but 2 cases by the CSM and 1 case by the CBM failed. Conclusions: Using the disposable membrane cell collector to process BPE of lung adenocarcinoma patients for RNA extraction and ALK gene detection is more effective and successful compared with the traditional methods, and it is suggested to be further applied and popularized in clinical practice.