We propose a scheme of building a free-electron laser in the soft X-ray region pumped by the soliton laser. Making use of soliton laser wave evolution shape and single-pass small signal analysis, we find that this laser has two special advantages over the previous electromagnetic wave undulator free-electron lasers namely, (1) a very small "mass-shift effect" because of the special characteristics of soliton lasers, (2) an additional "frequency tuning effect" based on the conventional free-electron laser's tuning ability. We also obtain the small signal gain and carry out some discussion.