Do you hold official/service passport? if not, You have to get an official invitation letter from the host institute in China and an original visa notice sheet from an authorized governmental apparatus /organization in China prescribing the visa validity, number of entries and stay period;

dear sir i request ur honor that i m government officer and i need travel by road from pakistan to china for private business purpose but i dont have an invitation letter please inform how i can apply

Your business partner can issue you the invitation letter and apply for the visa notification letter from an authorized chinese government office, if you don't have the business partner, you can't get the invitation letter.

I know you are government officer, but do you hold the official/service passport or regular passport, as I know, diplomatic/official/service passport holders of pakistan can visit China for up to 30 days without a visa.