5R-5-hydroxytriptolide (LLDT-8) is a new drug candidate which is in clinical trial treating rheumatoid arthritis.  Polymorph screening of the compound was carried out in this study.  Polymorph of LLDT-8 was prepared by evaporative crystallization and antisolvent crystallization methods and was characterized by powder X-ray diffraction (p-XRD), infrared spectrometry (IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TG).  It was found that p-XRD patterns, DSC curves, TG curves and IR spectra of the LLDT-8 samples prepared by the above recrystallization methods were all consistent.  The 2θ of main peaks in the p-XRD patterns appeared at 7.58°, 8.14°, 8.66°, 15.46°, 16.46°, 29.54°, 31.16° and 38.26°, while the infrared absorption peaks appeared at 3 471.3, 2 962.2, 2 887.0, 1 762.6, 1 677.8, 1 432.9, 1 365.4, 1 247.7, 1 080.0, 1 031.7 and 877.5 cm⁻¹.  LLDT-8 was decomposed at 271.2 ℃ based on the determination from DSC and TG.  It was showed in single crystal X-ray diffraction study that LLDT-8 crystal was monoclinic with the space group being P2 (1).  The cell parameters were found to be: a = 11.460 1 (11), b = 6.320 5 (6), c = 13.028 1 (12), α = 90.00, β = 115.557 (2) and γ = 90.00.  The crystal was a hydrogen-bonded dimmer.  The slurry experiments, which were further conducted in solvents with different polarities, confirmed the stability of solid state of LLDT-8 based on the p-XRD determination.  The polymorph of LLDT-8 made assurance of its efficacy consistence during its clinical trials.