Objective:To investigate change law of saccharides in Rehmanniae Radix Praeparata with different processing times based on metabolomics. Method:Samples processed by one to nine cycles of repeated steaming and drying with traditional method were collected

which were derived with 1-phenyl-3-methyl-5-pyrazolone(PMP)

then subjected to LC-MS analysis.The principal component analysis(PCA) and orthogonal partial least squares-discrimination analysis(OPLS-DA) were performed with SIMCA-P 13.0

then difference markers were obtained

meanwhile

which were identified by ion fragmentation and reference substance. Result:Six saccharides were identified by OPLS-DA

namely manninotriose

melibiose

mannose

glucose

galactose and arabinose.In which the relative peak areas of manninotriose and melibiose gradually reduced to 0.60 and 0.52 in ninth cycles

respectively;while arabinose had a increasing trend

the relative peak area was highest in ninth cycles and reached up to 4.74.Meanwhile

mannose firstly increased and then reduced

the relative peak area was 3.33 in fifth cycles and it was higher than other cycles;but glucose and galactose remained relatively stable.The score plot of PCA showed that Rehmanniae Radix Praeparata processed by 1 to 9 cycles gradually changed along the PC1 axis and saccharides were significant changed. Conclusion:The saccharides in Rehmanniae Radix Praeparata with different processing times are quite different.This paper can provide a reference for quality evaluation of Rehmanniae Radix Praeparata processed by nine cycles of repeated steaming and drying.