只需两步，rails支持CSV格式导出

一、Controller最上方添加 require 'csv'

二、方法里面添加

      format.csv do
        csv_string = CSV.generate do |csv|
            csv << ["Name", "Created At"]
            @people.each do |person|
                csv << [person.name, person.created_at]
            end
        end
        render :text => csv_string
      end

最终代码：

require 'csv'
class PeopleController < ApplicationController
  def index
    @people = Person.all
    respond_to do |format|
      format.html # index.html.erb
      # 对应url http://localhost:222/people.json
      format.json { render json: @people }
      # 对应url http://localhost:222/people.xml
      format.xml { render :xml => @people}
      format.atom { @feed_title = "My event list" } # index.atom.builder
      # 添加csv格式
      format.csv do
        csv_string = CSV.generate do |csv|
            csv << ["Name", "Created At"]
            @people.each do |person|
                csv << [person.name, person.created_at]
            end
        end
        render :text => csv_string
      end
    end
  end

最后浏览器http://localhost:3000/people.csv 不过用excel打开UTF-8格式的csv汉字会显示乱码，需要转换为GBK