A protection device for an oil-smoke sensor has a protection housing having two ends and an inner chamber; the first end having a first opening for receiving a probe of the oil-smoke sensor and in communication with the inner chamber; a second opening is disposed on the second end which is opposite to the first opening and in communication with the inner chamber. Because the probe is sealing mounted in the first opening, the probe will not be directly exposed in oil-smoke flow. The protective device is mounted such that the axial direction of the protective device is vertical to the oil-smoke flow direction. Therefore, the inner chamber of the protection housing has a pressure with respect to the oil-smoke flow that tangentially flows at a high speed, and the oil-smoke can only be diffused into the protection housing, thus, the probe is much less likely to be contaminated.