Operando time-resolved soft x-ray absorption spectroscopy (TR-SXAS) is an effective method to reveal the photochemical processes of metal complexes in solutions. In this study, we have developed the TR-SXAS measurement system for observing various photochemical reactions in solutions by the combination of laser pump pulses with soft x-ray probe pulses from the synchrotron radiation. For the evaluation of the developed TR-SXAS system, we have measured nitrogen K-edge x-ray absorption spectroscopy (XAS) spectra of aqueous iron phenanthroline solutions during a photoinduced spin transition process. The decay process of the high spin state to the low spin state in the iron complex has been obtained from the ligand side by N K-edge XAS, and the time constant is close to that obtained from the central metal side by time-resolved Fe K-edge XAS in the previous studies.