The sample of cristobalite including some impure elements was obtained by heating treatment of natural Changbaishan diatomite at 1450°C for 2h

and it was confirmed to be a single phase according to the powder X-ray diffraction and FTIR results. The high-pressure and high-temperature experiment of cristobalite was carried out at a pressure up to 63 GPa by symmetrical diamond anvil cell（DAC） apparatus and synchrotron radiation energy dispersive X-ray diffraction method at BSRF. The results indicate that cristobalite underwent serial phase transformations at up to 40 GPa

and at this pressure point

the new high-pressure phase of cristobalite is similar to the α-PbO

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type structure except a diffraction line at about 0.3798 nm. The diffraction modes of a series of high-pressure metastable phases of cristobalite have the successive characteristic

which maybe reflect the fact that the original structure of cristobalite is favorable for the formation of the post-stishovite structure. The sample was heated by YLF laser to about 1600 K at 40 GPa. After heating

the sample was transformed to a new structure which was similar to the stishovite structure

and the experimental pressure was lowered to 34.8 GPa. Then the sample was pressed to 62.9 GPa

and its structure has no change. After heating to about 1500 K at this pressure

the sample has no structural transformation

and the pressure fell to 53.9 GPa. The sample still keeps the stishovite-like structure after the pressure unloaded. The experimental results maybe provide some useful hues to discuss the formation mechanism of natural SiO

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post-stishovite phases.