原因就是你定位的时候那个endPos就是一个坐标差，不用.x，.x是undefined所以会回滚回去，
你最后的endPos*3 我也不知道什么意思。。

window.onload = function() {
            var startPos = null,
                endPos = null,
                slider = document.getElementById('slider');
            slider.style.width = slider.getElementsByTagName("li").length * parseInt(getStyle(slider.getElementsByTagName("li")[0], "width")) + "px";
            if (!!('ontouchstart' in window) || window.DocumentTouch && document instanceof DocumentTouch) {
                addEvent(self.slider, "touchstart", fnstart);
                addEvent(self.slider, "touchmove", fnmove);
                addEvent(self.slider, "touchend", fnend);
            }

            function fnstart(ev) {
                var touch = ev || event.targetTouches[0]; //touches数组对象获得屏幕上所有的touch，取第一个touch
                startPos =touch.pageX;
            }

            function fnmove(ev) {
                if (event.targetTouches.length > 1 || event.scale && event.scale !== 1) return;
                var touch = event.targetTouches[0];
                var slider=document.getElementById('slider');
                endPos =touch.pageX - startPos;
                event.preventDefault();
                var _trans=getTransform(slider);
                console.log(endPos+"+++++++"+Number(_trans));
                slider.style.transform = "translateX(" + (endPos+Number(_trans)) + "px)";
            }

            function fnend() {
                if (Math.abs(endPos) > 60) {
                    var slider=document.getElementById('slider');
                    var _trans=getTransform(slider);
                    console.log(endPos+"+++++++"+Number(_trans));
                    var juli=(Math.ceil(endPos/100)*100+Number(_trans));
                    if(juli<0){
                        juli=juli>screen.width-1600?juli:screen.width-1600;
                    }else{
                        juli=0;
                    }
                    slider.style.transform = "translateX("+ juli + "px)";
                }
            }
            
            function getTransform(_dom){
                var dom=_dom;
                var transform=dom.style.transform;
                
                if(transform!=""){
                    return transform.split("(")[1].split("px")[0];
                }
                else{
                    return 0;
                }
            }

            function getStyle(obj, attr) {
                if (obj.currentStyle) {
                    return obj.currentStyle[attr];
                } else {
                    return getComputedStyle(obj, false)[attr];
                }
            }

            function addEvent(obj, event, fn) {
                obj['bind' + event] = obj['bind' + event] || [];
                obj['bind' + event]['bind' + fn] = obj['bind' + event]['bind' + fn] || function() {
                    fn.call(obj);
                }
                if (typeof document.addEventListener != "undefined") {
                    obj.addEventListener(event, obj['bind' + event]['bind' + fn], true);
                } else {
                    obj.attachEvent('on' + event, obj['bind' + event]['bind' + fn]);
                }
            };
        }

实现了chrome版没有做其他兼容，主要问题就是你给transform赋值以及坐标的运算出问题了，你一直给他赋值endPos大概就是你这次滑动的距离，并不会累加