SDHC UHS-1 class 10 45MB/s compatibility with PANASONIC HMC-154ER camcorder

i couldnt record HD Video in HIGH quality on the card mentioned.

why?

the card is 300x speed, class 10, 45 MB/s while the camera manual states it need a class 6 cera, and the bitrate for high quality HD is 24MB/s variable.

Check with Panasonic. Some cameras look specifically for class 6 and even though class 10 is faster the cameras firmware may not recognize class 10 as a usable card for had video capture. It is possible they have a firmware update but if not you may be stuck using class 6 cards.