To study the relationship of inspiratory capacity (IC) with body mass index (BMI), fat free mass index (FFMI), and fat mass index (FMI) in adults with normal lung function.Based on a survey on the Chinese physiological constants conducted in Heilongjiang during 2008, we obtained the data of 2,050 adults (921 men and 1,129 women aged 19-81 years) with normal lung function and grouped them according to the standard of classification of body weight recommended by Working Group on Obesity of China. Statistical analysis was performed using Pearson correlation analysis, one-way analysis of variance,and multi-factor regression analysis.After the influences of age and gender were adjusted, IC was positively correlated with BMI, FFMI, and FMI in adults aged 19-81 years (all P= 0.000) (the correlation coefficients were 0.320, 0.303, and 0.204, respectively). The means of IC, FFMI, and FMI in obesity group were significantly higher than those in overweight group normal weight group, and underweight group, were significantly higher in overweight group than in normal weight group and underweight group, were significantly higher in normal weight group than in underweight group (all P = 0.000). Multiple stepwise regression analysis showed that factors including age, gender, height, FFMI, and FMI influenced IC, and while height, FFMI, and FMI were positively correlated with IC, gender and age were negatively correlated with IC.BMI, FFMI, and FMI are positively correlated with IC in adults with normal lung function. The elevation of IC derived from BMI may attribute to FFMI and FMI, and FFMI has a higher influence on IC than FMI does.