Mr.laxman rana, first, you should prepare the below documents for tourist visa application:
A. The original passport with at least six-month validity and two blank visa pages, one photocopy of the passport page containing the personal particulars.

B. Truly completed and signed Visa Application Form of the People's Republic of China. One recent passport-photo size color photograph of the applicant.

C. Invitation letter (if visit for the first time).
If the applicant cannot provide an invitation letter, please provide a visa recommendation letter from the applicant's employing company, organization, etc.

Other additional documents required according to the merits of each applicant, e.g. bank statements, round-trip air tickets booking, etc.

if you come to China for visiting family members, the Proof of relationship, photocopy of the identity document and residence permit of the relative in China are required

Usually, it takes four working days to issue the visa. If the visa is needed earlier, additional urgent fee will be charged.

for more information, please refer to http://np.china-embassy.org/eng/ConsularService/t555055.htm