The invention relates to a penetration test device and method for a pressure-variable head based on a laser measuring system, belonging to the relevant technical fields of geotechnical engineering. The device mainly comprises a penetration container, wherein the bottom of the penetration container is communicated with a seepage pipe, and a first valve and a second valve are mounted on the seepage pipe; the seepage pipe located between the first valve and the second valve is in tight communication with a measuring pipe, and a measuring reflecting float is put in the measuring pipe; and a laser sensor matched with the measuring reflecting float is arranged at the upper part of the measuring pipe and is used for transferring signals to a laser measuring processor. By utilizing a brand new structure, cohesive soil is subjected to penetration measurement by virtue of laser, and data can be measured and recorded in real time.