話不多說，上代碼，因為我的代碼也是拷貝別人的，只是在別人的基礎(chǔ)上改了點東西。

    var EARTH_RADIUS = 6378137.0;    //單位M 
    var PI = Math.PI; 
    function getRad(d){
        return d*PI/180.0;
    } 
    function getFlatternDistance(lat1,lng1,lat2,lng2){ 
        var f = getRad((lat1 + lat2)/2); 
        var g = getRad((lat1 - lat2)/2); 
        var l = getRad((lng1 - lng2)/2); 
        var sg = Math.sin(g); 
        var sl = Math.sin(l); 
        var sf = Math.sin(f); 
        var s,c,w,r,d,h1,h2; 
        var a = EARTH_RADIUS; 
        var fl = 1/298.257; 
        sg = sg*sg; 
        sl = sl*sl; 
        sf = sf*sf; 
        s = sg*(1-sl) + (1-sf)*sl; 
        c = (1-sg)*(1-sl) + sf*sl; 
        w = Math.atan(Math.sqrt(s/c));
        r = Math.sqrt(s*c)/w;
        d = 2*w*a;
        h1 = (3*r -1)/2/c;
        h2 = (3*r +1)/2/s;
        var _d= d*(1 + fl*(h1*sf*(1-sg) - h2*(1-sf)*sg));
        if(isNaN(_d)){ return 0 + 'm'; }
        _d = _d < 1000 ? parseInt(_d) + 'm'  : (_d*1000).toFixed(1) + 'km';
        return _d;
    }