In order to improve the integrated level of system and reduce the cost of measure, a high cost-effective and accurate measurement for the light scattering parameters of the super smooth optical surface is realized by using LabVIEW software to replace the hardware lock-in amplifier of measuring system. A photoelectric check system used for measuring light scattering are designed, the system is made up of light path, photoelectric detector, data acquisition and control system, the software for correlation detection algorithm etc. On that basis, the phase lock algorithm based on LabVIEW software platform is studied mainly in this paper. The technique for phase locked detection realized by software in the weak photoelectric signal detection is raised, and the technique is simulated. When measured signal frequency is 0.2 kHz, amplitude is 1.0 V and the noise amplitude is 0.5 V, the measurement error is 0.1%. The simulation result shows that the detection for the modulated weak photoelectric signal can be realized effectively by this method.