The invention discloses a water turbine integrated speed change box for a small-size sprinkling machine for gardens. The water turbine integrated speed change box comprises a supporting vertical plate (1), a water turbine box (2) and a speed change box (3), wherein the water turbine box and the speed change box are fixedly mounted on left and right vertical surfaces of the supporting vertical plate with a flat plate structure respectively; the water turbine box comprises a turbine shell body (21), a pressure water input connector (22), a pressure water output connector (23) and a water turbine (24); the water turbine comprises a blade (241), a wheel hub (242) and a turbine shaft (243); the turbine shaft penetrates through one end of the supporting vertical plate and stretches into the speed change box; and the speed change box comprises a speed change box shell body (31) and a transmission gear pair which is arranged in a containing cavity of a secondary transmission gear pair of the speed change box shell body (31). The water turbine integrated speed change box for the small-size sprinkling machine for the gardens is compact in structure and simple to control, can achieve the purpose that relatively high transmission efficiency is guaranteed under a relatively small volume, is convenient to maintain and service and is particularly suitable for the small-size sprinkling machine for the gardens.