Abstract: The national gravity network to be built is composed of 100 points,15 absolute gravity points and 85 relative gravity points,and nearly 200 observations.This paper evaluated the primary scheme firstly.Considered the target of optimization design for precision,reliability and cost,some principles that were suitable for gravity network designing were proposed.During the first order optimal designing,the simulative method was used to find and delete the observation which had little influence on the precision of the network.After that we got a scheme whose precision was little lower than that of being required.Based on this plan we used the analytic method and simulative method to do the second order optimal design and got tow schemes.Both of the schemes satisfied the requirement of precision and had a higher reliability and a lower cost relatively.