The invention discloses a lost pet positioning system based on big data; the advantages are that a positioning device outputs a position signal to a mobile phone according to a pet position; a positioning APP stores the position signal according to dates; when the pet is separated from the positioning device, the positioning device outputs an alarm signal to the mobile phone; the positioning APP outputs the position signal, the finally positioned position of the positioning device, and the time at which the positioning device and the pet are separated onto a cloud server; the cloud server calculates the probability of the pet missing direction and distance, packs the data into a searing direction packet, and outputs same to the positioning APP; the user searches the pet according to the probability of the pet missing direction and distance; if the pet drops the positioning device by itself, the pet can be analyzed and positioned according to behavior habit positions, thus fast findingthe lost pet; if the positioning device is removed by an outlaw, alarms are sent out; the police can acquire monitoring data surrounding a position at which the pet and the positioning device are separated, thus fast capturing the outlaw, and rescuing the trafficked pet.