A chair assembly comprising: a base; a supporting frame disposed above the base and including at least one supporting board extending perpendicularly to a ground, wherein the at least one supporting board includes a rear side having a first guiding groove, and wherein the first guiding groove including an inclined groove section extending rearwards and downwards; a backrest; a seat including a rear end pivotably connected to the backrest, permitting adjustment of a reclining angle of the backrest, wherein the rear end of the seat includes at least one lower guiding wheel corresponding to the first guiding groove, and wherein the seat further includes a front end having at least one front guiding wheel; an operating frame disposed below the seat and including at least one operating board disposed on a side of the at least one supporting board, wherein the at least one operating board includes a rear end having a second guiding groove and a front end having a third guiding groove, wherein the second guiding groove is aligned with and located on a side of the inclined groove section of the first guiding groove, wherein the at least one lower guiding wheel is movably received in the first guiding groove and the second guiding groove, wherein the third guiding groove has a slope different from a slope of the second guiding groove, and wherein the at least one front guiding wheel is movably received in the third guiding groove; and a first operating rod including two ends pivotably connected to the supporting frame and the seat, respectively, wherein when the first operating rod is in an extended position, the at least one lower guiding wheel is located in a front end of the first guiding groove and a front end of the second guiding groove, and the at least one front guiding wheel is located in a front end of the third guiding groove, and wherein when the first operating rod retracts, the at least one lower guiding wheel moves to a rear end of the first guiding groove and a rear end of the second guiding groove, the at least one front guiding wheel moves to a rear end of the third guiding groove, the seat moves rearwards, the rear end of the seat moves downwards while the seat is moving rearwards, and wherein the front end of the seat inclines upwards while the seat is moving rearwards. a base; a supporting frame disposed above the base and including at least one supporting board extending perpendicularly to a ground, wherein the at least one supporting board includes a rear side having a first guiding groove, and wherein the first guiding groove including an inclined groove section extending rearwards and downwards; a backrest; a seat including a rear end pivotably connected to the backrest, permitting adjustment of a reclining angle of the backrest, wherein the rear end of the seat includes at least one lower guiding wheel corresponding to the first guiding groove, and wherein the seat further includes a front end having at least one front guiding wheel; an operating frame disposed below the seat and including at least one operating board disposed on a side of the at least one supporting board, wherein the at least one operating board includes a rear end having a second guiding groove and a front end having a third guiding groove, wherein the second guiding groove is aligned with and located on a side of the inclined groove section of the first guiding groove, wherein the at least one lower guiding wheel is movably received in the first guiding groove and the second guiding groove, wherein the third guiding groove has a slope different from a slope of the second guiding groove, and wherein the at least one front guiding wheel is movably received in the third guiding groove; and a first operating rod including two ends pivotably connected to the supporting frame and the seat, respectively, wherein when the first operating rod is in an extended position, the at least one lower guiding wheel is located in a front end of the first guiding groove and a front end of the second guiding groove, and the at least one front guiding wheel is located in a front end of the third guiding groove, and wherein when the first operating rod retracts, the at least one lower guiding wheel moves to a rear end of the first guiding groove and a rear end of the second guiding groove, the at least one front guiding wheel moves to a rear end of the third guiding groove, the seat moves rearwards, the rear end of the seat moves downwards while the seat is moving rearwards, and wherein the front end of the seat inclines upwards while the seat is moving rearwards.