Abstract: Objective To evaluate the feasibility of treating pneumothorax with automatic intermittent decompression with micro-catheter instead of traditional thorax water sealed drainage (TWSD). Methods The automatic decompression instrument (ADI), which decompressed intermittently with programmed control, was designed and assembled by the authors (Patent No. ZL 01242081.6). A prospective study of the efficacy of this device was conducted in 87 pneumatothorax cases, and the results were compared with those of TWSD. Results The average time of closure in ADI group was 4.12±0.98 days, which was significantly shorter than that with TWSD (6.83±2.06 days, P<0.01). The incidence of complications was also significantly lower in ADI patients (P<0.01), and none of them developed severe complications. Clinical cure was achieved in all the patients in ADI group except for two patients who gave up treatment voluntarily and one transferred for open surgery. Conclusions Application of ADI allows faster healing and safer and easier operation, and causes fewer complications and less pain with shortened hospital stay as compared with conventional therapy for open and tension pneumothorax.