The　compounds　of　SmCo5　and　Sm0.8Tm0.2Co5.2　have　been　studied　via　X-ray　diffraction　(XRD)　and　magnetic　measurements,　in　order　to　clarify　the　effect　of　Tm　doping　on　the　crystal　structure　and　intrinsic　magnetic　properties　of　the　SmCo5　compound.　XRD　results　show　that　both　compounds　have　a　single　hexagonal　CaCu5　type　crystal　structure,　and　the　Tm　doping　leads　to　an　expansion　of　the　hexagonal　unit　cell　in　the　direction　of　c　axis　and　a　contraction　of　a,　b　axes　and　the　cell　volume.　The　Curie　temperatures　(T-C)　of　the　SmCo5　and　Sm0.8Tm0.2Co5.2　are　957　and　965　K,　respectively.　Magnetic　measurements　show　that　both　the　magnetic　anisotropy　field　(H-A)　and　the　magnetization　at　an　applied　field　of　7　T　(M-7T)　of　SmCo5　are　higher　than　those　of　Sm0.8Tm0.2Co5.2　at　room　temperature　(300　K).　However,　the　H-A　and　M-7T　of　SmCo5　become　lower　than　those　of　Sm0.8Tm0.2Co5.2　with　the　temperature　increasing　to　473　K.　Therefore,　it　is　concluded　that　Tm　doping　in　SmCo5　can　effectively　improve　the　magnetic　properties　at　elevated　temperature.