The invention provides a normal-pressure hot water boiler comprising a hearth, a fire grate and a heat exchange water tank. The fire grate is arranged below the hearth and is one of a reciprocating fire grate, a rolling fire grate and a chain fire grate. Four air blowers are arranged below the fire grate and are controlled by an intelligent system. The reciprocating fire grate is adopted as a combustion device of the normal-pressure hot water boiler, segmented forced air supply of a combustion area can be achieved through the air blowers below the fire grate, fire coal combustion can be promoted to be more sufficient, and smoke is little. The fire grate and the air blowers of the boiler are all controlled by the intelligent system, the automation degree is high, and economical operation can be achieved.