The relationship between surface-enhanced Raman scattering (SERS) power collected by the fiber Raman probe and sample position was investigated theoretically under the sample damage threshold limit by using ray tracing method. The results show that, in a given damage excitation power density threshold, the SERS power collected by the probe with different focal-length lens increases when the sample deviates from the focal plane. Furthermore, compared with the situation that the sample is away from the probe and deviate from the focal plane, SERS power collected by the probe is higher at the situation that the sample is close to the probe and deviates from the focal plane. In addition, the lager the collection fiber core diameter is, the greater the power collected by the probe will be.