Objective To provide a simplified and effective scale to measure self-reported physical function of cancer patients in China. Methods The PROMIS (v2.0) Physical Function Short Form 6b was translated into simplified Chinese and culturally adapted. Then 240 cancer patients were investigated to evaluate its psychometric properties. Results The Simplified Chinese version of PROMIS (v2.0) Physical Function Short Form 6b was a unidimensional scale containing 6 items. Confirmatory factor analysis supported a one-factor structure (χ2/df=2.260，CFI=0.983，TLI=0.971，SRMR=0.029，and RMSEA=0.072). The criterion validity using the physical functioning dimension of SF-36 as the criterion was 0.668 (P<0.01). The largest standardized residual covariance between items ranged from -0.349 to 0.184.The Rasch model explained 80.8% of the variance in the data. The item to total correlation coefficients ranged from 0.71 to 0.89, and the person reliability was 0.86. The item maps showed no overlap of the item difficulties. The Cronbach′s α coefficient was 0.892. Participants could complete the short form in 1.0 to 1.5 minutes. Conclusion The simplified Chinese version of PROMIS (v2.0) Physical Function Short Form 6b has acceptable construct validity, content validity, person reliability and criterion validity, and shows reasonable distribution of item difficulties. It also has satisfactory internal consistency reliability and is convenient for filling out. It can be used as a self-report measure of physical function of cancer patients in China.