Solved!!

when calling the pennies json-rpc, not parameter method like getblockcount result is ok, but parameter method like getblockhash report 500 error, request as below, please help, tks.
{"jsonrpc":"1.0","id":"1","method":"getblockcount"}
{"jsonrpc":"1.0","id":"1","method":"getblockhash","params":["0"]}