lz,你好，签证有如下分类和特点：
签证类别 基本材料 有效期 申请时间（工作日） 签证费用（RMB）
商务签证 邀请函原件,派遣函,保险，户口簿 1-3个月 3－7
旅游签证 经济证明，准假信户口簿，身份证 3个月 3－7 2500
探亲访友签证 正式邀请函，经济证明，准假信，户口簿 3个月 3－7
工作签证 公司证明，邀请函原件，户口簿， 依据工作时间 2－3个月
学生签证 录取通知书，资金证明，语言成绩，学习计划 依据学习时间 依据课程类别

下面给你两个样本（仅供参考）
（1）
(Salutation)

I would hereby invite the members of Beijing delegation totally
4 persons (listed attachment) led by you, to come over to ***
(country) for *** (exposition), which is to be held at *** (place)
during *** (date). Please make the necessary arrangements
for your delegation to arrive in *** (country). During the
exposition, you will stay here for *** days. All your
expenses including international air tickets, local
transportation, accommodations, medical insurances and
all other related expenses during your stay here will be paid
by yourselves.

We are looking forward to greeting you in *** (country) very
soon.

Yours sincerely,

(Signature)


（2）
June 25th,2007

TO:(邀请客户所在的公司)

ATTN: (客户的名字)

Re: Invitation for Business Trip

I, (你的名字), on behalf of (你公司的名字) Would like to invite 客户的名字to visit our office in 公司所在城市, China in the 日期.

The main purpose of this trip is to give you more ideas on business view here. At the same time to try implementing the agreement, which is under discussion/negotiation for some time.

All the traveling and accommodation expenses in China will be borne by your company.

Name:客户的名字
(passport number: 护照号码 )

Yours truly,


xxxx

然后公司盖上公章寄走即可,保险起见可以先扫描给客户看是否可以.

另外你也可以参考：

你可以参考修改一下，希望能够帮到你，好运@