nginx配置：

    keepalive_timeout 600; 

    proxy_send_timeout 600;

    client_max_body_size 200M;  

    fastcgi_connect_timeout 600;

    fastcgi_send_timeout 600;

    fastcgi_read_timeout 600;

    fastcgi_buffer_size 1024k;

    fastcgi_buffers 8 1024k;

    fastcgi_busy_buffers_size 1024k;

    fastcgi_temp_file_write_size 1024k;

    proxy_ignore_client_abort on;

    tcp_nopush on;

    tcp_nodelay on;

    client_header_timeout 600; 

    client_body_timeout 600; 

    sendfile on; 

    send_timeout 600;     

php的配置或php-fpm上传大小配置及post大小也需要修改

根据你的实际情况修改上边的配置吧

具体原因不清楚， 不过502错误一般都是PHP那边出了问题
不是没响应，就是响应时间过长，等。
这里已经和nginx没什么关系了

我在Xubuntu 14.04上用测试PHP CLI Server,只配置了下面两条,其他都是默认配置,就能上传90多MB的ZIP包了.

upload_max_filesize=100M
post_max_size=128M

php -S 127.0.0.1:8080 -t /png/www/example.com/public_html/
// chmod 777 /png/www/example.com/public_html/app/yab/static/
// http://127.0.0.1:8080/app/yab/upload.php
<?php
if(!empty($_FILES)){
    $uploaddir = '/png/www/example.com/public_html/app/yab/static/';
    $uploadfile = $uploaddir . basename($_FILES['userfile']['name']);

    echo '<pre>';
    if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
        echo "File is valid, and was successfully uploaded.\n";
    } else {
        echo "Possible file upload attack!\n";
    }

    echo 'Here is some more debugging info:';
    print_r($_FILES);

    print "</pre>";
    exit();
}
?>


<form enctype="multipart/form-data" action="./upload.php" method="POST">
    Send this file: <input name="userfile" type="file" />
    <input type="submit" value="Send File" />
</form>

输出:

File is valid, and was successfully uploaded.
Here is some more debugging info:Array
(
    [userfile] => Array
        (
            [name] => firefox.zip
            [type] => application/zip
            [tmp_name] => /tmp/phpG1PdtU
            [error] => 0
            [size] => 93938426
        )

)

同时本地测试了Nginx + PHP-FPM,Nginx只修改了下面这个配置:

client_max_body_size 128M;

经过我测试，上传文件是可以上传成功的，但是我用wget --post-file 就返回502错误
wget可能有限制大文件上传，
用curl命令搞定：
curl -T "msg.log" "http://192.168.1.148/upload.php"
谢谢大家 结贴！

nginx_module_upload

你把php的执行时间调大一点，另外上传超时也调大一点。
set_time_limit(),max_input_time之类的。你是不是第一次调完后再上传会等一会儿才报502错？