Dim nd1, nd2, nd3, nd4, nd5, nd6, nd7, nd8, nd9 As New TreeNode ‘这行正确
Dim nd(0 To 8) As TreeNode ’不能加New
nd1.Text = "切换用户" ‘这行正确
nd(2).Text = "系统设置" ’这行代码报错，请问怎么解决？

Dim nd1, nd2, nd3, nd4, nd5, nd6, nd7, nd8, nd9 As TreeNode
Dim nd(8) As TreeNode = {nd1,nd2,nd3,nd4,nd5,nd6,nd7,nd8,nd9}
nd1.Text = "切换用户"
nd(2).Text = "系统设置"
报错是因为你没有给nd这个数组赋值，里面的变量都是空的
另外你程序的写法也非常有问题，如果用数组，就别单独声明这么多变量
可以用这种方法
dim nd(8) as treenode
for i as integer = 0 to 8
nd(i) = new treenode
next