Ti5Si3/TiAl　composites　were　successfully　prepared　by　pressure　infiltration　and　subsequent　reactive　annealing.　Final　microstructure　of　Ti5Si3/TiAl　composites　was　dependent　on　the　reactive　annealing　temperature,　which　varied　from　1350　degrees　C　to　1420　degrees　C,　two　typical　microstructures　could　be　achieved:　(i)　An　unique　core-shell　structure　(Core:　fully　lamellar　alpha　2-Ti3Al/gamma-TiAl　with　in-situ　synthesized　Ti5Si3　particles　predominantly　distributed　at　the　interfaces　of　alpha　2/gamma　lamellar　colonies;　Shell:　equiaxed　gamma-TiAl　with　Ti5Si3　particles　distributed　in　gamma　grain　boundaries);　And　(ii)　A　novel　quasi-network　structure　composed　of　fully　lamellar　alpha　2/gamma　and　a　majority　of　Ti5Si3　particles　with　a　quasi-network　distribution.　The　formation　of　the　two　microstructures　could　be　attributed　to　the　chemical　composition　heterogeneity　which　was　caused　by　the　difference　in　interdiffusion　rate　of　Ti　and　Al　elements　in　different　annealing　temperatures.　The　comparative　investigations　on　high　temperature　tensile　properties　and　creep　behavior　showed　that　the　core-shell　Ti5Si3/TiAl　composites　exhibited　a　better　specific　strength　(165　MPa　center　dot　g-　1　center　dot　cm3)　and　higher　ultimate　tensile　strength　(633　MPa)　at　800　degrees　C,　which　was　12　%　higher　than　that　of　the　quasi-network　Ti5Si3/TiAl　composites.　While　the　creep　behavior　analysis　showed　that　in　compassion　with　equiaxed　gamma　phase,　the　slip　distance　of　dislocations　in　fully　lamellar　alpha　2/gamma　phase　was　shorter,　impeding　the　motion　of　dislocations　more　effectively.　And　core-shell　Ti5Si3/TiAl　composites　possessed　a　large　number　of　grain　boundaries　concentrating　in　the　shell　which　became　weaker　in　the　high　temperature,　facilitating　the　formation　of　creep　pores　in　the　shell　and　the　final　premature　fracture.　Hence,　the　quasi-network　Ti5Si3/TiAl　composites　containing　a　higher　content　of　fully　lamellar　alpha　2/gamma　exhibited　a　better　creep　resistance　than　that　of　core-shell　Ti5Si3/TiAl　composites.　More　importantly,　the　steady　state　creep　rate　at　750　degrees　C　under　the　fixed　stress　of　250　MPa　of　quasi-network　Ti5Si3/TiAl　composites　was　relatively　low,　only　3.305　x　10-8　s-　1,　comparable　to　that　of　third-generation　TiAl　alloys.