The present invention discloses an MEMS seawater conductivity sensor with a filtering device. The sensor comprises an insulating substrate, four metal electrodes and a filtering device. The filtering device is in the shape of rectangular box cover, the top surface of the filtering device is provided with a filtering hole array. The filtering device covers the upper end face of the insulating substrate through an edge part. A cavity formed between the filtering device and the insulating substrate is a conductivity cell. The four metal electrodes are arranged at the insulating substrate in the conductivity cell and are connected to an external testing circuit through lead wires. Compared with the prior art, the MEMS seawater conductivity sensor has the advantages that the shortcomings of poor anti-pollution ability and low measurement precision of an existing MEMS conductivity sensor are overcome, the MEMS seawater conductivity sensor has the advantages of simple structure, small size, low power, low cost, and versatility, and the real-time seawater conductivity measurement with high precision is conveniently realized.