Objective: To investigate the effects of continuous positive airway pressure（CPAP） treatment on insulin resistance （IR） in patients with type 2 diabetes and obstructive sleep apnea hypopnea syndrome（OSAHS）. Methods：Twenty-five patients with type 2 diabetes and OSAHS were recruited. Their apnea hypopnea index （AHI） was 37.7±18.0 with BMI maintained at 29.1 ± 2.3 kg／m2. The homeostasis model assessment（HOMA） index was used to reflect IR and measured before and after 6 months’ CPAP treatment. Results：The HOMA index was significantly lower following 6 months’ CPAP treatment than before treatment（1.84 ± 1.98 vs 3.33 ± 2.96, P < 0.0001）. Conclusion：CPAP treatment can significantly improved increased IR in OSAHS patients, which suggests that OSAS is an independent risk factor of IR.