Error: All configured authentication methods failed levels: 'client-authentication'

I am using node.js ssh2 module.I have installed ssh2 module by executing the command 'npm install ssh2'.However, when I use ssh2 to connect to a remote server, it always output the error: [Error: All configured authentication methods failed] levels: 'client-authentication'

This is my code

var Client = require('ssh2').Client
var conn = new Client();
var option = {
    host: '10.171.65.154',
    port: 22,
    username: 'root',
    password: '123456'
};

conn.on('ready', function(){
    console.log('Client :: ready');
    conn.sftp(function(err, sftp){
        if(err) throw err;
        sftp.readdir('home', function(err, list){
            if(err) throw err;
            console.dir(list);
            conn.end();
        });
    });
}).on('error', function(err){
    console.log(err);
}).connect(option);

However, I can not connect successfully.I am sure the username and password are correct and I can connect successfully by SecureCRT.

it always output the error: [Error: All configured authentication methods failed] levels: 'client-authentication'