Want to visit china next month? Whats the procedure?

If you will stay at your brother's place, you need an invitation letter from him, together with copies of his residence permit, work visa, relationship documents attested by Ministry of Foreign Affairs of Pakistan, and passport bio data page. BTW, you'd better prepare an air ticket for leaving China.

Does inviation letter needs to be in specific format. Attestation from china required

No, there is no specific format, but make sure include Personal information of the applicant, such as name, gender,and date of birth; Purpose of the visit to China, travel itinerary such as date of entry and exit, places of visit, relationship between the inviter and the applicant, and who will bear the expenses of the applicant in China.
BTW, the financial guarantees are helpful.

Your brother need to write invitation letter for you with full Personal informations. also he need to get "official confirmation of invitation letter" from Shanghai Municipal foreign affairs office and must send you both letters in ORIGINAL to get your China visa from Pakistan.