The BIP32 Extended Keys are different? I was using the same random entrophy (d2310508c6c5313795dc80a7408b608ffda7176dbedefac00f8114c5dd89a673) to generate the BIP32 Root ExtendedKey (path: m) in the libbitcoin-explorer and web-based wallet respectively.

But I don't know why i got two different results?

In the libbitcoin-explorer, I typed the command (./bx hd-new d2310508c6c5313795dc80a7408b608ffda7176dbedefac00f8114c5dd89a673) and got:
xprv9s21ZrQH143K4bPcDZFCnACLDrv2ta2XUpPyMU2j98VEpw1XPPTt7oPiQbbXscESmatehXLGGUGLRZ5yYBiN2y2VR1q6pmH69YBuDWkqW1f

In the web based wallet I had:
 xprv9s21ZrQH143K4EQpRE59bbF9QXCW7QxJSW4LF9wWWWJCamtjVqnn5yuQGh9Y3XDAr9NSwyszLGjqXCuVc3gYMgRjy7FrW12MuaBY5jc4jVu
Because they are doing two different things.

libbitcoin is taking the entropy and directly using it as a BIP 32 seed to produce the BIP 32 master private key.

However the web based wallet is taking the entropy, producing a BIP 39 mnemonic, then using the BIP 39 mnemonic to produce the BIP 32 seed and from there the master private key. Since BIP 39 mnemonic to BIP 32 seed involves hashes and does not result in the same value used to create the mnemonic, the resulting BIP 32 seed is different from your initial entropy. Thus you are getting two different private keys.