To solve the practical problems such as poor long-term stability and large zero drift of clock-type vector magnetometer, mutual interference and high component noise of integrated suspended spherical coils, a proton vector magnetometer based on split-suspension spherical coil is proposed. The measuring principle and instrument structure are emphatically introduced. In addition, a new type of lowcost simple observation chamber is designed, and an one-year comparative observation experiment is implemented at Mengcheng seismic station using the two successfully developed prototypes. Results show that, total field noise, horizontal component noise and magnetic declination noise of prototype Ⅰ are 0. 23 nT, 0. 24 nT, and 2. 97″, and those values of prototype Ⅱ is 0. 28 nT, 0. 26 nT, and 3. 29″, which are lower than the average noise level of national network. The total field noise and horizontal component noise of prototype Ⅰ are better than the lowest noise of the network. The maximum horizontal components baseline deviation of two prototypes in a year is 6. 5 nT and 4. 7 nT, respectively. The maximum baseline deviation values of magnetic declination are 0. 67′ and 0. 54′, which are obviously lower than the baseline deviation average level of clock-type vector magnetometer of the network. The proton vector magnetometer based on split-suspension spherical coil has great stability.