【Objective】 To investigate the effect of trehalose added to M-Sol on platelet preservation at 4℃ in vitro. 【Methods】 Seven bags of ABO homotype concentrated platelets were randomly selected and divided into 7 groups according to storage temperature, preservation medium and trehalose concentration: 22℃+ PRP group, PRP group, M-Sol+ PRP group, M-Sol+ PRP+ 1 g/L trehalose group, M-Sol+ PRP+ 5 g/L trehalose group, M-Sol+ PRP+ 15 g/L trehalose group and M-Sol+ PRP+ 25 g/L trehalose group. PRP group and M-Sol preservation groups were stored at 4℃. Plt, PDW, MPV, maximum aggregation, CD62p positive rate, GLU and LAC concentration were detected on the 1st, 3rd, 5th and 7th day after preservation, and the changes of GLU and LAC concentration within 7 days were calculated. 【Results】 With the extension of preservation time, Plt decreased in all groups, and there was no significant difference among groups at the same time (P>0.05). PDW and MPV increased in all groups. When preserved to the 7th day, the PDW 10.22±0.43(fL) and MPV 8.74±0.40(fL) of M-Sol+ PRP+ 5 g/L trehalose group were the lowest, which was significantly different from that of 22℃+ PRP group (P0.05). During the preservation period, the maximum aggregation degree of each group decreased gradually. Except for the PRP group, the maximum aggregation degree of the M-Sol+ PRP+ 5g/L trehalose group was the highest(27.29±6.62), which was significantly higher than that of the 22℃+ PRP group on the 7th day after preservation (P<0.05). On the 7th day after preservation, the positive rate of CD62p in M-Sol+ PRP+ 5g/L trehalose group was the lowest(15.46±2.46), and there was significantly different compared with other groups (P<0.05). 【Conclusion】 Adding appropriate concentration of trehalose to M-Sol can inhibit platelet activation at 4℃ and reduce platelet storage lesion.