Abstract: Objective To explore the efficacy and safety of concurrent chemoradiotherapy with different timing of radiotherapy for locally advanced nonsmall cell lung cancer（NSCLC）. Methods Sixty NSCLC patients were randomly divided into four groups. All the patients received chemotherapy first（paclitaxel 120mg／m2iv d1, d8; cisplatin 75-80mg／m²ⁱv d₁). Twentyone days was a cycle， and 4 cycles were applied. And then combined with radiotherapy（1.8-2.0Gy／f，once per day，five times per week，DT 60Gy） in the treatment after the first cycle（group A）， the second cycle（group B）， the third cycle（group C） and the fourth cycle（group D） respectively. The efficacy and side effects were observed among four groups. Results The efficacy of the four groups was 92.3％， 71.4％， 60.0％ and 46.7％. The main side effects were radioactive esophagitis， myelosuppression， fatigue and alopecia. The incidence rate of grade 3-4 side effects in group A was higher than those of other groups， and had significant difference compared with group C and group D. Conclusion Radiotherapy combined with chemotherapy at early stage can achieve better effect companied by higher side effects in the treatment of locally advanced NSCLC. The therapeutic regimen should be considered in clinic.