Guangling Wang your procedure appears to be correct, in that you are post-fixing with 4%PFA for 48 h and then dehydrate in sucrose 30%. How thin are your sections you are cutting? You can try making your frozen sections a little bit thicker to avoid fragmentation. Also, try getting your cryostat blade sharpened. A dull blade can cause fragmentation.

Finally, you can try sequentially dehydrating your sample in 10% > 20% >30% sucrose baths for 2 days each instead to see if it will help.

thank you for Anton Fomenko's suggestions.The section's thin was 50um and my cryostat blade was a new one.I will try sequentially dehydration and hope for success.

We had a good experience with embedding 300 micron section into the gelatin and then cutting 40micron using vibrotome. In my hands, the cryostat never really worked for this.

Thanks ,Natalia. I have try to embedded 300 um section into 2% Agarose ,before using cryostat .It's difficult to let the section level in the agarose ,so can't get good slices.can you tell me your experiences ,please?