The invention belongs to measuring instruments, and particularly relates to a well logging density sensor used for measuring underground liquid density in petroleum drilling. The well logging density sensor is matched with a transmitter to constitute a well logging instrument special for measuring density. The well logging density sensor comprises a pair of high pressure connectors used for allowing fluid to flow in and out, a platinum resistor temperature sensor, fixed pressing blocks, an outer shell, a measuring tube, a first detector, a second detector, a vibration exciter, fixed pressing plates and locating rings. The well logging density sensor has the advantages that according to the technical scheme, the cylindrical outer shell, the fixed pressing blocks, the fixed pressing plates, the two locating rings and the like which are integrally processed are adopted, the structure is simplified, the overall rigidity is improved, and mounting, adjusting and maintaining can be achieved more conveniently. Experiments show that the sensor is stable in measuring result, good in repeatability and linearity, and the degree of accuracy is high after temperature compensation. The well logging density sensor thoroughly solves the problem that an existing well logging instrument is inconvenient to use and difficult to repair and maintain while a radioactive source is used for measuring density.