Compromised lung function is a common feature of COPD patients, but certain factors increase the rate of lung function decline in COPD patients. The objective of the current study was to investigate the effect of different clinically important factors responsible for rapid deterioration of lung function quantified as ≥ 60 ml decline in FEV1 over a period of one year. COPD patients recruited from the chest clinic of Penang hospital were followed-up for one year from August 2018 to August 2019. Rapid deterioration of lung function was defined as greater than 60 ml/year decline in force expiratory volume in one second. Among 367 included patients 73.84% were male, with mean age 65.26 (9.6) years and % predicted FEV1 51.07 (11.84). 30.27% patients showed mean decline of ≥ 60 ml in FEV1. The regression analysis showed that current smoking relative risk (RR) = 2.38 (1.78-3.07), p < 0.001); GOLD Stage III& IV RR = 1.43 (1.27-1.97), p < 0.001); mMRC score 3 to 4 RR = 2.03 (1.74-2.70), p < 0.01); SGRQ-C score ≥ 10 points difference RR = 2.01 (1.58-2.73), p < 0.01); SGRQ-C symptoms Score ≥ 10 points difference RR = 1.48 (1.23-2.29), p < 0.001); 6MWT < 350 m RR = 2.29 (1.87-3.34), p < 0.01); ≥ 3 exacerbation in study year RR = 2.28 (1.58-2.42, p < 0.001); 8 or more hospital admission days (RR = 3.62 (2.66-4.20), p < 0.001); Charlson comorbidity index ≥ 3 RR = 3.18 (2.23-3.76), p < 0.01) and emphysema RR = 1.31 (1.15-1.79), p < 0.01) were significant risk factors for the rapid deterioration of lung function (FEV1 decline ≥ 60 ml). Among different factors CCI score ≥ 3, abrupt decline in health status, exacerbation frequency ≥ 3, hospital admission days ≥ 8 and emphysema were reported as risk factors for rapid deterioration of lung function.