Abstract: A new type penetrometer named strip penetrometer is proposed. The strip penetrometer has the same advantages of other full-flow penetrometers with less end effect, and it is also applicable to detecting undrained strength of shallow soil. The shallow penetration test results of strip penetrometer are introduced. The motion modes of soils in the tests are analyzed. The lower bound solution at the shallow-deep transforming depth is established based on the numerical simulation. The virtual stress fields and kinematically admissible velocities are proposed as the penetrometer penetrates shallowly, and the lower and upper bounds are solved. The upper and lower limit strengths of soil test are compared with the vane shear strength. The results of the strip penetrometer fit well with the test ones.