I find your answer and finally convert it to phoenix 1.7, thank you How to convert this simple view to a Phoenix 1.7 view?
here’s my solution:

defmodule ExcelWeb.PostController do
  use ExcelWeb, :controller

  def index(conn, _params) do
    posts=[
      %{id: 1, name: "first", title: "first", content: "first"},
      %{id: 2, name: "second", title: "second", content: "second"},
      %{id: 3, name: "third", title: "third", content: "third"}
    ]

    conn
    |> put_resp_content_type("text/xlsx")
    |> put_resp_header("content-disposition", "attachment; filename=posts_report.xlsx")
    |> render("report.xlsx", %{posts: posts})
  end
end

defmodule ExcelWeb.PostXLSX do
  alias Elixlsx.{Workbook, Sheet}

  @header [
    "ID",
    "Name",
    "Title",
    "Content"
  ]

  def report(posts) do
    report_generator(posts)
    |> Elixlsx.write_to_memory("report.xlsx")
    |> elem(1)
    |> elem(1)
  end

  def report_generator(%{posts: posts}) do
    rows = posts |> Enum.map(&(row(&1)))
    %Workbook{sheets: [%Sheet{name: "Posts", rows: [@header] ++ rows}]}
  end

  def row(post) do
    [
      post.id,
      post.name,
      post.title,
      post.content
    ]
  end
end

and remember add the format in Myapp_web.ex

formats: [:html, :json, :xlsx]