The invention provides an oil-spraying preventing breather device of a diesel engine. The oil-spraying preventing breather device comprises a breather cover, a filter net, an oil gas guide pipe and an oil collector. Exhaust holes are distributed in the breather cover. The breather cover is in sealing connection with the oil collector through a thread. The oil collector is of a conical structure. A spiral oil trough spirally downward is distributed in the conical inner wall of the oil collector, and oil outlet holes are distributed in the bottom of the oil collector. The filter net is located on an inner conical support structure of the oil collector. The oil gas guide pipe is fixedly connected with the oil collector, and the stretching height of the part, in the oil collector, of the oil gas guide pipe can be adjusted. The oil-spraying preventing breather device has the beneficial effects that the rapid centrifugal guiding and separating function of the oil gas mixture is achieved, separated engine oil rapidly flows to the bottom of the oil collector through the spiral oil trough, and gas is evaporated through the filter net and exhausted through the exhaust holes of the breather cover; and for an engine with a large oil content in the oil gas mixture passing a breather system, the separation effect of the device is obvious, and the problem of oil spraying of the breather is solved.