Recently, port disturbance and mooring disturbance caused by oscillation has been seen as a problem at many ports and harbors, and fishing ports. The authors clarified the mechanism of port disturbance generation at Kumaishi fishing port, based on field observation and numerical simulation. However, the limit wave height which cause mooring disturbance on small fishing boats has not been clarified. The authors have analyzed mooring limit focusing on long-period wave heights based on past disasters exempla and the numerical simulation results. Conclusions below have been obtained from the analysis. (1) Mooring disturbance accompanied by the pass of low-pressure or typhoon, which damage ship bodies and require evacuations to other ports, occur several times a year at Kumaishi Fishing port. (2) From the hydrographic conditions in case of mooring disturbance, it is clarified that the mooring disturbance occur in case where H_1/3, which is the inrushing long-period wave height, is over 2.0m and H_L is over 0.10m. It is also clarified that the limit for long-period wave for small fishing boats is 0.25m since long-period wave inside the port is amplified 2.5-fold on these cases. (3) From the frequency of long-period wave inrushing to Kumaishi fishing port, it has been clarified that hydrographic conditions whose H_L is over 0.10m is 5.75% through a year and it is 14.71% in winter, which is the greatest value in the year. (4) The quantitative indicator "H_1/3 (over 2.0m)" has been introduced as a decision indicator for evacuations.