The　general　number　field　sieve　(GNFS)　is　asymptotically　the　fastest　algorithm　known　for　factoring　large　integers.　One　of　the　most　important　steps　of　GNFS　is　to　select　a　good　polynomial　pair.　Whether　we　can　select　a　good　polynomial　pair,　directly　affects　the　efficiency　of　the　sieving　step.　Now　there　are　three　linear　methods　widely　used　which　base-m　method,　Murphy　method　and　Kleinjung　method.　Base-m　method　is　to　construct　polynomial　based　on　the　m-expansion　of　the　integer,　Murphy　method　mainly　focuses　on　the　root　property　of　the　polynomial　and　Kleinjung　method　restricts　the　first　three　coefficients　size　of　the　polynomial　in　a　certain　range.　In　this　paper,　we　compare　the　size　property　and　root　property　of　the　polynomials　which　select　from　the　three　methods.　A　good　leading　coefficient　a(d)　of　f(1)　is　important.　The　good　means　that　a(d)　has　some　small　prime　divisors.　Kleinjung　method　does　not　give　a　concrete　method　to　choose　a　good　a(d)　in　its　first　step.　We　choose　these　better　a(d)　first　and　store　in　a　set　A(d),　then　take　the　A(d)　as　input.　Through　the　pretreatment　we　can　get　better　polynomial　and　speed　up　the　efficiency　of　Kleinjung　method　at　the　same　time.