A novel precise force measurement based on a Y-shaped cavity dual-frequency laser is proposed. The principle of force measurement with this method is analyzed, and the analytic relation expression between the input force and the change in the output beat frequency is derived. Experiments using a 632.8-nm Y-shaped cavity He-Ne dual-frequency laser are then performed; they demonstrate that the force measurement is proportional to a high degree over almost five decades of input signal range. The maximum scale factor is observed as 5.02 \times 10^9 Hz/N, with beat frequency instability equivalent resolution of 10^{-5} N. By optimizing the optical and geometrical parameters of the laser sensor, a force measurement resolution of 10^{-6} N could be expected.