Hello,
I'm doing some test of Dash on testnet, but it generates bitcoin-like address such as "17HGVKGNHUW2TYoC3jrEf2rSV6Xeyd7NuM" which starts with 1. But, address of Dash-testnet starts with "y" such as "yPwTggY8JEFaDjAgUdHmapG4SmzY6SDbE9".

I think the reason is that the magic value in Dash testnet is different from Dash mainnet. The magic value in mainnet is 76, and in testnet is 140 (https://dashpay.atlassian.net/wiki/spaces/DOC/pages/47742983/Testnet).