A　space　power　with　high　power　density,　light　weight,　low　cost　and　high　reliability　is　of　crucial　importance　to　future　exploration　of　deep　space.　Space　reactor　is　an　excellent　candidate　because　of　its　unique　characteristics　of　high　specific　power,　low　cost,　strong　environment　adaptability　and　so　on.　Among　all　types　of　space　reactors,　heat　pipe　cooled　space　reactor,　which　adopts　the　passive　heat　pipe　as　core　cooling　component,　is　considered　as　one　of　the　most　promising　choice　and　is　widely　studied　all　over　the　world.　A　transient　analysis　code　(TAPIRS)　for　heat　pipe　cooled　space　reactor　power　system　is　developed.　The　TAPIRS　based　on　point　reactor　kinetics　model,　lumped　parameter　core　heat　transfer　model,　combined　heat　pipe　(HP)　model　(self-diffusion　model,　flat-front　startup　model　and　network　model),　energy　conversion　model　of　alkali　metal　thermal-to-electric　conversion　units　(AMTEC).　and　HP　radiator　model.　Three　typical　accidents,　i.e.,　control　drum　failure,　AMTEC　failure　and　partial　loss　of　the　heat　transfer　area　of　radiator　arc　then　analyzed　using　TAPIRS.　The　results　show　that　the　heat　pipe　cooled　space　reactor　has　excellent　inherent　safety　characteristics.