Provided are a method and a system for photovoltaic-series compensation system time-domain simulation small disturbance analysis. The method comprises: based on a preset small disturbance time-domainsimulation model, determining series compensation degree of a series compensation circuit; according to the series compensation degree of the series compensation circuit, determining the number of capacitors, continuously putting the capacitors whose number is determined into the system in a phased manner, to perform time-domain simulation small disturbance analysis; based on a single photovoltaicpower generation unit equivalent simplified model, the preset small disturbance time-domain simulation model establishing. The technical scheme can preferably analyze mechanism of subsynchronous oscillation on system, and provides effective inhibition measures for the oscillation mechanism.