The invention belongs to the technical field of solar energy, and particularly discloses a horizontal rotating mechanism and a heliostat system. The horizontal rotating mechanism comprises a fixing seat, a rotary seat, a rotary disc, a first rotary arm, a second rotary arm, a horizontal driving assembly; the rotary seat is connected with the fixing seat in a pin joint mode; the rotary disc is arranged above the rotary seat, and is fixedly connected with the rotary seat; the first rotary arm is arranged on one side of the rotary seat, and one end of the first rotary arm is connected with the rotary disc in a pin joint mode; the second rotary arm is arranged on the other side of the rotary seat, one end of the second rotary arm is connected with the other end of the first rotary arm in a pinjoint mode, and the other end of the second rotary arm is connected with the fixing base in a pin joint mode; and the horizontal driving assembly comprises a push rod and a push rod driving assemblywhich are connected with each other, the push rod driving assembly drives the push rod to move in the axial direction of the push rod, one end of the push rod is connected with the push rod driving assembly, the other end of the push rod is connected with the first rotary arm, and the push rod driving assembly is connected with the fixing seat in a pin joint mode. According to the horizontal rotating mechanism and the heliostat system, the horizontal rotating range can be expanded, and the horizontal rotating stability can be improved.