A　ring-cavity　synchronously-pwnped　optical　parametric　oscillator　was　investigated,　which　was　pumped　by　a　self-mode-Iocked　Ti:sapphire　laser.　A　periodically　poled　KTiOPO4　crystal　was　used　in　the　oscillator,　and　the　parametric　operation　was　obtained.　The　wavelength　of　the　signal　wave　covered　from　1000　nm　to　1500　nm.　The　signal　wave　was　successfully　frequency　doubled　by　inserting　a　nonlinear　BBO　crystal　in　the　cavity.　The　wavelength　of　second　harmonic　could　be　tuned　from　550　nm　to　650　nm　freely　by　cavity-length　tuning.　The　loss　of　the　cavity　and　the　threshold　of　the　pump　power,　a　thin　glass　substrate　is　inserted　into　the　cavity　to　couple　output　the　light,　then　the　output　power　is　measured　for　varying　pump　power,　based　on　the　measurement　the　loss　in　the　cavity　was　discussed.　Furthermore,　the　characteristic　of　output　pulses　is　also　measured.